Magneto-optic disk exhibiting a phase shift between plus and minus twelve degrees and a reflectivity between fifteen and twenty-five percent

Abstract

An optimal structure for a quadrilayer magneto-optic data storage medium is described. The structure has superior characteristics of signal to noise, reflectivity, ellipticity, write sensitivity, and stability.

Description

BACKGROUND OF THE INVENTION

This invention relates to magneto-optic recording media which are capable of storing digital information by means of the thermal magnetic recording principle.

Several structures have been used in fabricating magneto-optic data storage media. One of the simplest structures, shown in FIG. 1, includes a substrate 12, a magneto-optic layer 11, and a first dielectric layer 10. As with the other structures discussed below, the magneto-optic layer is typically a polycrystalline thin film of MnBi, MnSb, MnCuBi, or MnTiBi; an amorphous rare earth-metal alloy such as TbFeCo, GdCo, GdFe, TbFe, GdTbFe, DyFe, or TbDyFe; or a multilayer film such as alternating thin films of Pt and Co. As shown in FIG. 1, the magneto-optic layer is sandwiched between a substrate material and a dielectric layer to provide a storage function based on the direction of magnetization in different regions of the magneto-optic layer. The digital information stored in magneto-optic layer 11 is read by directing a polarized laser beam 2 through dielectric layer 10 to magneto-optic layer 11, where it is partially reflected. An external lens (not shown) focuses laser beam 2 on magneto-optic layer 11. Depending on the magnetization direction of the segment of magneto-optic layer 11 from which laser beam 2 is reflected, the polarization direction of the reflected portion of laser beam 2 will rotate through either a positive or a negative angle, as a result of the Kerr effect. An external sensing device (not shown) reads the information stored in magneto-optic layer 11 by detecting the direction of the angular rotation of the reflected laser beam 2.

Several characteristics are significant in evaluating the performance of a magneto-optic storage medium. Among these are the signal-to-noise ratio of the reflected light beam, the ease of writing on the medium, the reliability of the medium in storing data, the susceptibility of the magneto-optic layer to corrosion, the prevention of interference from dust particles on the surface of the medium, and the reflectivity of the medium, which is important for tracking purposes.

While the structure shown in FIG. 1 is relatively easy to construct, it is vulnerable to interference from dust particles on the upper surface of dielectric layer 10, and its signal-to-noise performance is less than desirable. An improved signal-to-noise ratio is exhibited by the quadrilayer structure shown in FIG. 2, which includes a second dielectric layer 13 and a metallic reflecting layer 14 sandwiched between magneto-optic layer 11 and substrate 12. Reflecting layer 14 typically consists of a thin film of a metal such as Al, Cu, Ag or Au. In this structure, the portion of laser beam 2 which passes through magneto-optic layer 11 and second dielectric layer 13 is reflected at the surface of reflecting layer 14. Provided that the thickness of second dielectric layer 13 is set properly, the portions of laser beam 2 that are reflected at the interface of magneto-optic layer 11 and second dielectric layer 13 and the interface of second dielectric layer 13 and metal reflecting layer 14, respectively, interfere constructively so as to magnify the Kerr rotation of the reflected light, thereby improving the signal-to-noise ratio.

FIG. 3 shows an alternative structure which has the additional advantage of being less susceptible to interference from dust contamination. The structure shown in FIG. 3 is identical to that shown in FIG. 2, except that substrate 12 is positioned on the side of the quadrilayer stack upon which the laser beam is incident. Layers 10, 11, 13 and 14 function in the same manner as in the arrangement of FIG. 2. A particle of dust on the upper surface of substrate 12 is far above the focal point of laser beam 2, which is in magneto-optic layer 11. Therefore, unless the particle is extremely large, it will not affect the performance of the disk. Furthermore, if substrate 12 and first dielectric layer 10 are made of materials which have refractive indexes of approximately 1.5 and 2, respectively, the positioning of first dielectric layer 10 immediately beneath substrate 12 will help to reduce the portion of laser beam 2 (not shown) which is reflected before it reaches magneto-optic layer 11. This leads to a stronger reflected signal. Also, first dielectric layer 10 acts as a barrier to protect magneto-optic layer 11 from corrosion as a result of humidity or contamination from substrate 12. This quadrilayer structure realizes almost the same improved signal-to-noise performance as the structure of FIG. 2.

Despite the improvements inherent in the quadrilayers shown in FIGS. 2 and 3, until now structures of this type which have been designed to maximize the signal-to-noise ratio have exhibited a low degree of reflectivity, often in the range of 4 to 6%, and often an unacceptably large phase shift in the magneto-optically rotated reflected light. The servomechanisms used in disk drives for automatic focusing and tracking of the laser beam at present require a reflectivity in the range of 15 to 25%, preferably about 20%.

Phase shift in the reflected light occurs when the respective components of the reflected light parallel and perpendicular to the polarization direction of the incident beam are not in phase, resulting in elliptical polarization. Such phase shift (or ellipticity) in the reflected signal creates detection problems. If .phi. represents the phase shift of the reflected light, i.e., the phase difference between the magneto-optic reflected light component and the normal reflected light component, the performance of the information reading operation varies in proportion to cos .phi.. Therefore, a value of .phi. equal to zero is ideal, but a value of .phi. in the range of about -12.degree. to +12.degree. is considered satisfactory.

Although optical retardation plates are available to reduce or eliminate ellipticity, the utility of an individual plate is limited to a particular value of .phi.. Hence, retardation plates are not a practical solution to the problem, since the value of .phi. may vary widely between different storage media. Therefore, the multilayer structure has to be made so that the phase shift .phi. is essentially zero in order to ensure interchangeability among different media and drives.

Several studies have attempted to find an optimum quadrilayer structure in terms of the composition and thickness of each layer. See, for example, articles entitled "Design Concept of Magneto-Optical Disk", by Tamada et al., Internal Symposium on Optical Memory, Sept. 26-28, 1989, Kobe, Japan, p. 83; "Magneto-optical disk with reflecting layers", Ohta et al., SPIE, Vol. 382, p. 252, 1983; "High quality magneto-optical disk", by Takahashi et al., SPIE, Vol. 695, p. 65, 1986, all of which articles are incorporated herein by reference in their entirety.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide an improved quadrilayer magneto-optic storage medium.

Another object of this invention is to provide a magneto-optic storage medium in which the ellipticity of the reflected light is minimized; the reflectivity of the structure is in the desirable range of 15% to 25%; the signal-to-noise ratio is maximized; the write power sensitivity is in the appropriate range (less than 16 mW of laser power for a pulse width of 50 nS); and the stability of the information stored in the medium is high even after long periods of continuous readout and under adverse magnetic fields.

A further object of this invention is to provide a quadrilayer magneto-optic medium which, in addition to the foregoing advantages, allows information to be recorded at a high density on the medium.

In a quadrilayer magneto-optic storage medium fabricated according to this invention, the composition and thicknesses of the dielectric layers, the magneto-optic layer and the metallic reflecting layer are adjusted so as to optimize the reflectivity, signal-to-noise ratio, ellipticity, ease of writing and stability characteristics of the structure, as described above. Among other things, the dielectric layer adjacent the reflecting layer consists of a thin layer (no more than about 400 .ANG. thick) formed of a material having a low thermal conductivity. The thickness of the metallic reflective layer is adjusted so as to minimize heat dissipation during the writing operation while providing sufficient reflectivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates in cross section the structure of a bilayer magneto-optic storage medium.

FIG. 2 illustrates in cross section the structure of a quadrilayer magneto-optic storage medium fabricated with the supporting substrate on the side away from the incident laser beam.

FIG. 3 illustrates in cross section the structure of a quadrilayer magneto-optic storage medium fabricated with the supporting substrate on the same side as the incident laser beam.

FIG. 4 contains a graph showing the reflectivity and thermal conductivity of Al-Ti and Al-Ta alloys as compared with pure Al.

DETAILED DESCRIPTION OF THE INVENTION

We have found that certain quadrilayer structures in which the thickness of the dielectric layer adjacent the metal reflecting layer is in the range of (A) 50-400 .ANG., or (B) 50-400 .ANG. plus one-half the wavelength of the incident light, have very desirable levels of reflectivity and phase shift. This has been found true for structures in which the metal reflective layer consists of Al, Cu, Ag or Au and in which the dielectric layer adjacent the metal reflective layer has a refractive index of 1.4 or more. (Referring to FIGS. 2 and 3, first dielectric layer 10 will sometimes be referred to hereinafter simply as the "first dielectric layer" and second dielectric layer 13 will sometimes be referred to simply as the "second dielectric layer.")

In reality, dielectric layer thicknesses in the range of condition (B) above are not practical. Since the wavelength of the incident light beam is typically on the order of 8000 .ANG. in vacuum, condition (B) would require a second dielectric layer 13 thickness in the range of 2000-4000 .ANG.. Fabrication of such a layer is not practical because it would require an excessive deposition time which might also result in an excessive temperature rise in the storage disk during sputtering. In addition, the expense of fabricating such a layer would be formidable.

A different problem attends the use of a second dielectric layer having a thickness of only 50-400 .ANG., as in condition (A) above. A second dielectric layer of this small dimension might allow excessive heat transfer from the magneto-optic layer to the metal reflecting layer during data recording. The heat absorbed by the highly heat-conductive metal reflecting layer would quickly diffuse over a wide area. Thus, if the thickness of the second dielectric layer is too small, the result might be to widen the recorded bit area, prevent high density recording and require high laser power for writing.

This problem is known to those familiar with this art. For example, the Tamada et al. article cited above recognizes that the ellipticity of the reflected light becomes "smaller for thinner [second] SiN [dielectric] layer," but because of "intersymbolic interference between written pits," which renders the stack "not suitable for higher density recording," Tamada et al. settle on a compromise thickness of 500 .ANG. for second dielectric layer. Takahashi et al., cited above, experimented with a second dielectric layer 250 .ANG. thick, but the reflectivity of their medium was only about 10%, which is substantially lower than necessary for effective tracking.

We have found that unacceptable results such as these can be avoided by taking the following steps. First, the second dielectric layer is constructed of an amorphous or other material which has a low thermal conductivity (less than 0.06 Joules/sec-cm-.degree.K). Examples of such materials are ZrO.sub.2 --Y.sub.2 O.sub.3 --Al.sub.2 O.sub.5 mixture, SiO.sub.2 and ZnS. Second, the thickness of the metal reflecting layer is reduced to the point where lateral heat dissipation is minimized while the layer continues to provide an adequate reflective function. The metal reflecting layer can consist of, for example, Al, Cu, Ag or Au, in pure form or alloyed with other metals. An Al alloy with a few percent (1%-6%) of Ti or Ta is particularly suitable, since these alloys have a thermal conductivity which is substantially lower than that of pure Al, while their reflectivity is essentially the same (see FIG. 4). This further reduces lateral heat conduction in the metal reflecting layer.

Where the metal reflecting layer is exposed, a dielectric layer 15 may be added to protect the metal reflecting layer, as shown in FIG. 3. Dielectric layer 15 may preferably consist of an amorphous or other material such as a ZrO.sub.2 --Y.sub.2 O.sub.3 --Al.sub.2 O.sub.5 mixture, SiO.sub.2 or ZnS. All of the dielectric layers may be deposited by RF magnetron or RF diode sputtering, reactive sputtering or ion beam plating.

The characteristics of a quadrilayer storage medium constructed in accordance with this invention depend on the composition and thickness of each layer. While the discussion has focused on the characteristics of the second dielectric and metallic layers in particular, an optimized quadrilayer structure requires that the characteristics of the first dielectric layer and the magneto-optic layer otherwise be adjusted so as to bring them into an advantageous relationship with the other layers.

A preferred embodiment of the invention has been fabricated with a sputtering system which uses three stationary targets: the first target consists of 85 wt. % of ZrO.sub.2, 5 wt. % of Y.sub.2 O.sub.3 and 10 wt. % of Al.sub.2 O.sub.5 (wt. % represents percentage by weight) (this material is designated "ZYA" and is described in U.S. patent application Ser. No. 07/582,719, now abandoned, incorporated herein by reference); the second target consists of 21.5 at % of Tb, 83.5 at % of Fe and 5 at % of Co (at % represents atomic percentage); the third target is Al. The targets are typically 8 inches in diameter. Disks of glass, polycarbonate or another suitable substrate material are transferred from one target to another and coated with an appropriate thickness of the target material. The ZYA target is initially sputtered using an RF magnetron at 1.0 kW in an argon atmosphere of 4 mTorr for 73 seconds, producing a first dielectric layer ZYA about 550 .ANG. thick. The argon pressure is then increased to about 5 mTorr, and the Tb.sub.21.5 Fe.sub.83.5 Co.sub.5 target is sputtered using an RF diode at 0.4 kW for 75 seconds, producing a magneto-optic layer of TbFeCo about 300 .ANG. thick. A second dielectric layer of about 120 .ANG. in thickness is then deposited by sputtering the ZYA target with an RF magnetron at 0.4 kW for 36 seconds at 4 mTorr. The metal layer is formed at a thickness of 350 .ANG. by sputtering the Al target with a DC magnetron at 0.5 kW for 24 seconds in a 5 mTorr argon atmosphere. Finally, the ZYA target is RF magnetron-sputtered at 1.0 kW for 53 seconds to produce a 370 .ANG. thick protective layer (argon pressure is again 4 mTorr). The specifications and results of the foregoing process are summarized in Table 1.

TABLE 1__________________________________________________________________________ NominalLayer Argon Sputter Sputter LayerNo. Pressure Power Time Thickness(FIG. 3) Target Composition (mTorr) (kW) (sec) (.ANG.)__________________________________________________________________________10 Zirconia.sub.85 Yttria.sub.5 4 RF magnetron-1.0 73 550 Alumina.sub.10 weight % (ZYA)11 Tb.sub.21.5 Co.sub.5 Fe.sub.83.5 At % 5 RF diode-0.4 75 30013 ZYA 4 RF magnetron-0.4 36 12014 Aluminum 5 DC magnetron-0.5 24 35015 ZYA 4 RF magnetron-1.0 53 370__________________________________________________________________________

Magneto-optic storage media fabricated in this manner have been found experimentally to have a reflectivity of about 20%, a very small ellipticity of the reflected beam, and a high signal-to-noise ratio. The writing power is 10 mW to 13 mW using pulse widths of 50 nS to 80 nS, a focusing lens with a numerical aperture of 0.53, and a writing magnetic field of 300 Oe. The properties of this medium are summarized in Table 2.

TABLE 2______________________________________Reflectivity (R) 19% to 21%Figure of merit (K) which 7.3 .times. 10.sup.-3 to 8.5 .times. 10.sup.-3is equal to .crclbar..sqroot.R, where.crclbar. is the magneto-opticKerr rotationWrite Power (50 ns pulses 10 mW to 13 mWand magnetic field of 300 OeCarrier/Noise ratio (in 5 30 dBMHz bandwidth, on land, witha read power of 1.5 mW)______________________________________

The process of sputtering can also be performed in a commercial in-line sputtering system such as the ULVAC Model No. SM008C or SM018C manufactured by ULVAC of Japan. In this type of sputtering system, a chamber contains a series of sputtering targets past which the substrate is moved sequentially. The process specifications would be as described above.

Beyond the specific embodiment which has just been described, we have found a range of structures (i.e., layer thicknesses and refractive indices) which exhibit highly acceptable characteristics, that is, a high ratio of signal-to-noise, low phase shift, proper reflectivity and write power sensitivity, and capable of sustaining a high density of recording. In identifying the range of structures which have these desirable characteristics, we were guided by computer calculations based on known mathematical relationships concerning the interaction of circularly polarized light normally incident on a multi-layer film structure. The basic computation calculates the Fresnel reflection and transmission coefficients at each interface between the layers given the thickness and complex index of refraction of each layer. From the Fresnel coefficients, the reflectivity and transmission of the multilayer structure, the absorption in each of the layers, the figure of merit of the total structure, and the phase shift between the two polarization components are calculated. As noted, these relationships are known in the art and are discussed, among other places, in articles entitled "Signal and noise in magneto-optical readout", Mansuripur et al., Journal of Applied Physics, Vol. 53, No. 6, June 1982; "Magneto-optical disk with reflecting layers", Ohta et al., SPIE, Vol. 382, p. 252, 1983; and "Design and Characterization of a Quadrilayer Magneto-Optic Disk", McDaniel et al., IEEE Transactions on Magnetics, Vol. 24, No. 6, November 1988. Each of the foregoing articles is incorporated herein by reference.

A copy of the computer program we used is enclosed as Appendix A.

Tables 3-9 contain illustrations of structures that have been determined to possess desirable characteristics through computations performed with this program. In the tables,

x(t)=the thickness of the first dielectric layer (.ANG.) MO=the thickness of the magneto-optic layer (.ANG.) x(b)=the thickness of the second dielectric layer (.ANG.) m=the thickness of the metal reflecting layer (.ANG.) n.sub.1 =the refractive index of the first dielectric layer n.sub.2 =the refractive index of the second dielectric layer n.sub.mo =the refractive index of the magneto-optic layer R=the reflectivity of the structure (%) K=the magneto-optic figure of merit of the structure. K=.crclbar..sqroot.R, where .crclbar. is the magneto-optic Kerr rotation. .phi.=the phase shift (degrees) Vsat=.sqroot.R.multidot.100 .vertline.K.vertline..multidot. cos .O slashed..multidot.Vsat is proportional to the amplitude of the readout signal.

In Tables 3 and 4, the metal reflecting layer is an Al layer 400 .ANG. thick, and the refractive index of the first and second dielectric layers is 2.1 (e.g., ZYA).

In Table 5, the metal reflecting layer is an Al layer 400 .ANG. thick, the refractive index of the first dielectric layer is 2.1, and the refractive index of the second dielectric layer is 1.5.

In Tables 6 and 7, the metal reflecting layer is a Cu layer 400 .ANG. thick, and the refractive index of the first and second dielectric layers is 2.1.

In Table 8, the metal reflecting layer is a Cu layer 400 .ANG. thick, the refractive index of the first dielectric layer is 2.1, and the refractive index of the second dielectric layer is 1.5.

In Table 9, the metal reflecting layer consists of Al, and the refractive index of both dielectric layers is 2.0. This table clearly demonstrates that the overall optical properties of the structure do not deteriorate appreciably when the metal reflecting layer is made very thin.

In each of the tables, the magneto-optic layer has principal refractive indices of 3.72+i3.88 and 3.62+i3.83.

The manner of using the tables will be evident to those skilled in the art. For example, if it is desired to determine the characteristics of a quadrilayer structure which includes a metal reflecting layer Al 400 .ANG. thick; a magneto-optic layer having the above principal refractive indices and 300 .ANG. thick, a first dielectric layer having a refractive index of 2.1 (ZYA) and 750 .ANG. thick; and a second dielectric layer of ZYA and 100 .ANG. thick, Table 3 indicates that this structure will have a reflectivity R=19%, a figure of merit K=6.9.times.10.sup.-3, a phase shift .O slashed.=-6.degree., and Vsat=0.302 (see arrow). If the thickness of the dielectric layer is increased from 750 .ANG. to 850 .ANG., the reflectivity and figure of merit will remain the same while the phrase shift .O slashed. will fall to -1.degree. and Vsat will increase to 0.304.

While the invention has been described with respect to specific embodiments, those skilled in the art will appreciate that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, a variety of deposition techniques may be used to form the various layers of a magneto-optic storage medium. In addition, materials other than those listed may be used for the magneto-optic layer, the first and second dielectric layers, and the metal reflecting layer. Other layers may also be incorporated into a magneto-optic storage medium, e.g., to facilitate adhesion of the various structures within the device. Accordingly, all such changes come within the scope of this invention.

TABLE 3__________________________________________________________________________MO = 200.ANG. 250.ANG. 300.ANG. 350.ANG.x(t) x(b) R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat__________________________________________________________________________50 100 38 4.9 11 0.301 37 5.2 -2 0.315 37 5.2 -10 0.311 37 5.1 -17 0.298 200 32 5.6 -2 0.326 33 5.7 -14 0.318 34 5.5 -22 0.300 36 5.2 -27 0.278 300 27 6.4 -15 0.321 30 6.0 -25 0.302 33 5.7 -31 0.278 36 5.2 -36 0.254 400 24 6.7 -26 0.299 29 6.2 -34 0.276 32 5.7 -39 0.251 35 5.2 -42 0.230250 100 36 5.2 9 0.306 35 5.4 -3 0.328 35 5.4 -12 0.322 35 5.3 -29 0.298 200 29 6.0 -5 0.325 32 5.9 -16 0.316 32 5.7 -24 0.296 34 5.4 -30 0.275 300 25 6.6 -17 0.315 28 6.2 -27 0.295 31 5.8 -34 0.271 34 5.4 -38 0.249 400 22 6.9 -29 0.287 27 6.4 -37 0.266 31 5.9 -42 0.243 34 5.4 -45 0.223250 100 33 5.4 8 0.310 32 5.7 -4 0.320 32 5.7 -14 0.312 33 5.6 -22 0.297 200 27 6.3 -6 0.323 28 6.2 -18 0.312 30 6.0 -26 0.293 31 5.7 -31 0.272 300 22 6.8 -19 0.306 26 6.5 -29 0.287 29 6.1 -36 0.265 31 5.7 -40 0.244 400 20 7.2 -31 0.273 24 6.7 -39 0.255 28 6.2 -44 0.234 31 5.6 -46 0.216350 100 30 5.7 7 0.312 29 6.0 -5 0.319 29 6.0 -15 0.311 29 5.9 -22 0.296 200 23 6.6 -7 0.317 25 6.5 -19 0.307 27 6.3 -27 0.288 28 6.0 -32 0.266 300 19 7.2 -21 0.295 23 6.8 -31 0.278 26 6.4 -37 0.258 28 6.0 -41 0.239 400 17 7.5 -33 0.258 21 7.0 -41 0.243 25 6.5 -45 0.226 28 5.9 -48 0.211450 100 27 6.0 8 0.310 26 6.3 -5 0.317 26 6.3 -15 0.309 26 6.2 -22 0.293 200 20 6.9 -7 0.309 22 6.8 -19 0.301 23 6.6 -27 0.284 25 6.3 -33 0.265 300 16 7.5 -20 0.282 19 7.1 -31 0.269 22 6.7 -37 0.252 25 6.3 -42 0.235 400 14 7.8 -33 0.244 18 7.3 -41 0.233 22 6.8 -46 0.220 25 6.2 -48 0.207550 100 24 6.3 9 0.304 23 6.6 -3 0.312 23 6.6 -13 0.305 23 6.5 -21 0.291 200 17 7.2 -5 0.300 19 7.1 -17 0.294 20 6.9 -26 0.280 22 6.6 -31 0.263 300 14 7.7 -18 0.272 16 7.4 -29 0.262 12 7.0 -36 0.249 22 6.6 -40 0.234 400 11 8.0 -32 0.232 15 7.6 -40 0.227 19 7.2 -45 0.217 22 6.5 -47 0.206650 100 22 6.5 12 0.297 20 6.8 -0 0.307 20 6.8 -10 0.302 21 6.7 -18 0.291 200 15 7.4 -1 0.291 16 7.3 -14 0.289 IS 7.1 -23 0.278 20 6.8 -29 0.264 300 12 7.9 -14 0.263 14 7.6 -26 0.259 17 7.3 -33 0.249 19 6.8 -38 0.236 400 09 8.2 -26 0.226 13 7.8 -37 0.225 16 7.3 -42 0.219 19 6.8 -45 0.209750 100 21 6.6 17 0.289 20 6.9 4 0.303 .fwdarw.19 6.9 -6 0.302 19 6.8 -14 0.292 200 15 7.5 5 0.286 25 7.4 -9 0.289 17 7.2 -18 0.281 18 6.9 -25 0.269 300 11 8.0 -7 0.262 13 7.8 -21 0.263 15 7.4 -29 0.255 18 7.0 -33 0.244 400 08 8.3 -19 0.229 12 8.0 -31 0.232 15 7.5 -38 0.227 17 6.9 -41 0.219850 100 22 6.5 21 0.284 20 6.8 9 0.302 19 6.9 -1 0.304 20 6.8 -9 0.298 200 15 7.4 10 0.286 16 7.4 -3 0.293 17 7.2 -13 0.289 18 6.9 -20 0.278 300 11 8.0 -1 0.268 13 7.8 -14 0.272 15 7.4 -23 0.267 17 7.0 -28 0.256 400 09 8.3 -11 0.240 12 8.0 -25 0.246 14 7.5 -32 0.242 17 7.0 -36 0.233950 100 24 6.3 24 0.281 22 6.7 12 0.303 21 6.7 3 0.309 21 6.7 -5 0.305 200 17 7.2 14 0.290 17 7.3 1 0.301 18 7.1 -9 0.299 19 6.8 -15 0.290 300 13 7.8 5 0.279 14 7.6 -9 0.286 17 7.3 -28 0.281 19 6.9 -24 0.272 400 10 8.2 -5 0.258 13 7.8 -19 0.264 16 7.4 -27 0.260 18 6.9 -31 0.2501050 100 26 6.1 26 0.281 24 6.4 14 0.306 24 6.5 5 0.314 24 6.4 -3 0.312 200 20 7.0 16 0.297 20 7.0 4 0.311 21 6.9 -6 0.310 22 6.6 -13 0.301 300 15 7.6 7 0.294 17 7.4 -6 0.301 19 7.1 -15 0.296 21 6.7 -21 0.284 400 12 7.9 -2 0.279 15 7.6 -15 0.284 18 7.2 -23 0.277 20 6.7 -28 0.2651150 100 30 5.8 26 0.281 28 6.1 15 0.309 27 6.2 6 0.318 27 6.1 -2 0.317 200 23 6.7 17 0.305 23 6.7 5 0.320 24 6.6 -5 0.318 25 6.3 -11 0.308 300 18 7.3 8 0.308 20 7.1 -5 0.314 22 6.8 -14 0.307 24 6.4 -19 0.293 400 15 7.7 -1 0.298 18 7.3 -13 0.300 21 6.9 -21 0.291 23 6.4 -26 0.276__________________________________________________________________________ Reflecting layer is Al 400.ANG. thick n.sub.1 = n.sub.2 = 2.1 n.sub.me = 3.72 + i3.88 and 3.62 + i3.83 TABLE 4__________________________________________________________________________MO = 150.ANG. 200.ANG. 250.ANG. 300.ANG.x(t) x(b) R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat__________________________________________________________________________50 0 53 2.9 37 0.169 48 3.7 25 0.231 44 4.3 14 0.274 41 4.6 4 0.297 100 41 4.4 25 0.257 38 4.9 11 0.301 37 5.2 -1 0.315 37 5.2 -10 0.311 200 32 5.6 13 0.309 32 5.8 -2 0.326 33 5.7 -14 0.318 34 5.5 -22 0.300 300 25 6.6 1 0.324 27 6.4 -15 0.321 30 6.0 -25 0.302 33 5.7 -31 0.278150 0 52 3.0 35 0.177 46 3.9 24 0.240 42 4.5 13 0.282 39 4.8 3 0.302 100 39 4.6 24 0.265 36 5.2 9 0.306 35 5.4 -3 0.318 35 5.4 -12 0.312 200 29 5.9 12 0.312 29 6.0 -5 0.325 31 5.9 -16 0.316 32 5.7 -24 0.296 300 23 6.7 -2 0.329 25 6.6 -17 0.325 28 6.2 -27 0.295 31 5.8 -34 0.271250 0 49 3.2 35 0.185 43 4.1 23 0.248 39 4.7 12 0.289 37 5.2 2 0.308 100 36 4.9 23 0.271 33 5.4 8 0.310 32 5.7 -4 0.320 32 5.7 -14 0.312 200 26 6.1 10 0.321 27 6.3 -6 0.323 28 6.2 -18 0.312 30 6.0 -26 0.293 300 20 7.0 -3 0.311 22 6.8 -19 0.306 26 6.5 -29 0.287 29 6.1 -36 0.265350 0 46 3.4 34 0.193 40 4.4 22 0.256 36 5.0 11 0.295 33 5.4 1 0.311 100 33 5.2 22 0.275 30 5.7 7 0.312 29 6.0 -5 0.319 29 6.0 -15 0.311 200 23 6.5 9 0.307 23 6.6 -7 0.317 25 6.5 -19 0.307 27 6.3 -27 0.288 300 17 7.3 -4 0.298 19 7.2 -21 0.295 23 6.8 -31 0.278 26 6.4 -37 0.258450 0 43 3.7 34 0.199 37 4.6 23 0.260 33 5.3 11 0.297 30 5.7 1 0.322 100 30 5.5 23 0.275 27 6.0 8 0.310 26 6.3 -5 0.317 26 6.3 -15 0.309 200 20 6.7 10 0.298 20 6.9 -7 0.309 22 6.8 -29 0.301 23 6.6 -27 0.284 300 14 7.6 -3 0.282 16 7.5 -20 0.282 29 7.1 -31 0.269 22 6.7 -37 0.252550 0 40 3.9 35 0.202 34 4.9 24 0.261 30 5.6 13 0.297 27 6.0 2 0.311 100 27 5.7 25 0.270 24 6.3 9 0.304 23 6.6 -3 0.312 23 6.6 -13 0.305 200 18 7.0 13 0.286 17 7.2 -5 0.300 19 7.1 -17 0.294 20 6.9 -26 0.280 300 12 7.8 0 0.266 14 7.7 -18 0.271 16 7.4 -29 0.262 19 7.0 -36 0.249650 0 38 4.1 37 0.200 32 5.1 26 0.258 28 5.8 15 0.293 25 6.2 5 0.307 100 25 5.9 27 0.261 22 6.5 12 0.297 20 6.8 -0 0.307 20 6.8 -10 0.302 200 16 7.1 17 0.273 15 7.4 -1 0.292 16 7.3 -14 0.289 18 7.1 -23 0.278 300 10 8.0 6 0.252 12 7.9 -14 0.263 14 7.6 -26 0.259 17 7.3 -33 0.249750 0 37 4.1 39 0.195 31 5.2 29 0.252 27 5.9 18 0.287 24 6.3 9 0.303 100 24 5.9 31 0.252 21 6.6 17 0.289 20 6.9 4 0.303 19 6.9 -6 0.302 200 16 7.2 22 0.263 25 7.5 5 0.286 15 7.4 -9 0.289 17 7.2 -18 0.281 300 10 8.0 23 0.245 11 8.0 -7 0.262 13 7.8 -21 0.263 15 7.4 -29 0.255850 0 38 4.1 42 0.188 32 5.1 32 0.244 27 5.8 22 0.281 24 6.3 13 0.300 100 25 5.9 35 0.242 22 6.5 21 0.284 20 6.8 9 0.302 19 6.9 -1 0.304 200 17 7.1 27 0.257 15 7.4 10 0.286 16 7.4 -3 0.293 17 7.2 -13 0.289 300 11 7.9 20 0.245 11 8.0 -1 0.268 13 7.8 -14 0.272 15 7.4 -23 0.267950 0 39 4.0 44 0.180 33 5.0 34 0.237 29 5.7 25 0.276 26 6.1 16 0.299 100 27 5.7 38 0.236 24 6.3 24 0.262 22 6.7 12 0.303 21 6.7 3 0.309 200 19 6.9 31 0.256 17 7.2 14 0.290 17 7.3 1 0.301 18 7.1 -9 0.299 300 13 7.7 24 0.252 13 7.8 5 0.279 24 7.6 -9 0.286 17 7.3 -18 0.2821050 0 42 3.8 45 0.172 36 4.7 36 0.230 32 5.4 26 0.272 29 5.8 18 0.298 100 30 5.4 39 0.232 26 6.1 26 0.282 24 6.4 14 0.306 24 6.5 5 0.314 200 22 6.6 32 0.259 20 7.0 16 0.297 20 7.0 4 0.311 21 6.9 -6 0.310 300 16 7.4 26 0.264 15 7.6 7 0.294 17 7.4 -6 0.301 19 7.1 -15 0.2961150 0 45 3.5 46 0.166 39 4.5 36 0.225 35 5.1 27 0.269 32 5.5 18 0.296 100 34 5.1 39 0.229 30 5.8 26 0.281 28 6.1 15 0.309 27 6.2 6 0.318 200 25 6.3 33 0.265 23 6.7 17 0.305 23 6.7 5 0.320 24 6.6 -5 0.318 300 19 7.1 26 0.277 18 7.3 8 0.308 20 7.1 -5 0.314 22 6.8 -14 0.307__________________________________________________________________________ Reflecting layer is Al 400.ANG. thick n.sub.1 = n.sub.2 = 2.1 n.sub.me = 3.72 + i3.88 and 3.62 + i3.83 TABLE 5__________________________________________________________________________MO = 200.ANG. 250.ANG. 300.ANG. 350.ANG.x(t) x(b) R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat__________________________________________________________________________50 100 39 4.9 12 0.300 37 5.2 -0 0.315 37 5.2 -9 0.312 37 5.1 -17 0.300 200 32 5.8 -0 0.327 33 5.7 -12 0.322 35 5.5 -20 0.304 36 5.2 -26 0.283 300 28 6.3 -11 0.329 31 6.0 -21 0.311 33 5.7 -29 0.287 36 5.3 -33 0.263 400 25 6.7 -20 0.317 29 6.2 -29 0.293 33 5.8 -35 0.267 35 5.3 -39 0.244150 100 36 5.1 10 0.305 35 5.4 -2 0.318 35 5.4 -11 0.313 35 5.3 -19 0.299 200 30 6.0 -2 0.328 31 5.9 -14 0.320 33 5.7 -22 0.301 34 5.4 -28 0.280 300 26 6.5 -13 0.324 29 6.2 -24 0.305 31 5.9 -31 0.281 34 5.5 -36 0.258 400 23 6.9 -22 0.307 27 6.4 -32 0.284 31 6.0 -38 0.260 33 5.5 -42 0.237250 100 33 5.4 9 0.310 32 5.7 -3 0.322 32 5.7 -23 0.314 33 5.6 -20 0.299 200 27 6.3 -4 0.326 28 6.2 -16 0.317 30 6.0 -24 0.298 31 5.7 -30 0.277 300 23 6.8 -15 0.317 26 6.5 -26 0.298 29 6.1 -33 0.275 31 5.7 -37 0.253 400 22 7.2 -25 0.295 25 6.7 -34 0.274 28 6.2 -40 0.252 31 5.7 -43 0.231350 100 30 5.7 8 0.322 29 6.0 -4 0.321 29 6.0 -24 0.323 29 5.9 -21 0.297 200 24 6.6 -5 0.321 25 6.5 -17 0.312 27 6.3 -25 0.294 28 6.0 -31 0.273 300 20 7.1 -16 0.307 23 6.8 -27 0.290 26 6.4 -34 0.269 28 6.0 -39 0.249 400 18 7.5 -26 0.282 22 7.0 -36 0.264 25 6.5 -41 0.244 28 6.0 -45 0.226450 100 27 6.0 9 0.310 26 6.3 -4 0.318 26 6.3 -14 0.310 26 6.2 -21 0.295 200 21 6.9 -4 0.314 22 6.8 -17 0.306 23 6.6 -25 0.289 25 6.3 -31 0.270 300 17 7.4 -16 0.295 20 7.1 -27 0.282 22 6.8 -34 0.263 25 6.3 -39 0.245 400 15 7.8 -26 0.267 18 7.3 -36 0.254 22 6.8 -42 0.238 25 6.3 -45 0.222550 100 24 6.3 10 0.305 23 6.6 -2 0.314 23 6.6 -12 0.307 23 6.5 -20 0.293 200 18 7.2 -2 0.304 19 7.1 -15 0.299 20 6.9 -24 0.285 22 6.6 -30 0.268 300 14 7.7 -14 0.284 27 7.4 -26 0.274 19 7.1 -33 0.259 22 6.6 -38 0.243 400 12 8.0 -24 0.255 16 7.6 -35 0.247 19 7.2 -41 0.234 21 6.6 -44 0.221650 100 22 6.5 13 0.297 21 6.8 1 0.308 20 6.8 -9 0.304 21 6.7 -17 0.292 200 16 7.4 2 0.295 17 7.3 -12 0.295 18 7.1 -21 0.284 20 6.8 -27 0.269 300 12 7.9 -9 0.275 15 7.7 -22 0.271 17 7.3 -30 0.259 19 6.9 -35 0.245 400 10 8.2 -19 0.248 13 7.8 -31 0.245 16 7.4 -38 0.235 19 6.9 -41 0.224750 100 21 6.6 18 0.290 20 6.9 5 0.304 19 6.9 -5 0.303 20 6.8 -13 0.294 200 15 7.4 7 0.290 16 7.4 -7 0.293 17 7.3 -16 0.286 18 7.0 -23 0.274 300 12 8.0 -3 0.272 13 7.8 -17 0.273 16 7.4 -26 0.264 18 7.0 -31 0.252 400 09 8.3 -12 0.246 12 8.0 -26 0.249 15 7.5 -33 0.243 17 7.0 -37 0.232850 100 22 6.5 22 0.284 20 6.8 9 0.302 20 6.9 -1 0.306 20 6.8 -9 0.299 200 16 7.4 12 0.288 16 7.4 -1 0.297 17 7.2 -11 0.293 IS 7.0 -18 0.282 300 12 7.9 3 0.276 14 7.8 -11 0.281 16 7.4 -20 0.275 17 7.0 -26 0.264 400 10 8.3 -5 0.257 12 8.0 -19 0.261 15 7.5 -27 0.256 17 7.0 -32 0.246950 100 24 6.3 25 0.281 22 6.7 13 0.304 21 6.8 3 0.310 22 6.7 -5 0.306 200 18 7.2 16 0.292 18 7.3 3 0.304 18 7.1 -7 0.303 20 6.8 -14 0.293 300 14 7.7 8 0.286 15 7.6 -6 0.293 17 7.3 -15 0.289 19 6.9 -22 0.278 400 11 8.1 1 0.272 13 7.8 -14 0.278 16 7.4 -22 0.273 18 6.9 -28 0.2621050 100 27 6.1 27 0.280 25 6.4 15 0.306 24 6.5 6 0.315 24 6.4 -2 0.313 200 22 6.9 18 0.298 20 7.0 5 0.313 21 6.9 -4 0.313 22 6.6 -11 0.304 300 16 7.5 11 0.298 17 7.4 -3 0.307 19 7.1 -12 0.302 21 6.7 -19 0.290 400 14 7.9 4 0.290 16 7.6 -10 0.296 18 7.2 -19 0.289 20 6.7 -24 0.2761150 100 30 5.8 27 0.280 28 6.1 16 0.309 27 6.2 6 0.319 27 6.1 -1 0.317 200 24 6.6 19 0.305 23 6.7 6 0.321 24 6.6 -3 0.321 25 6.3 -10 0.311 300 19 7.2 11 0.311 20 7.1 -2 0.319 22 6.8 -11 0.313 24 6.4 -17 0.300 400 16 7.6 5 0.307 18 7.3 -9 0.311 21 6.9 -17 0.302 23 6.4 -23 0.287__________________________________________________________________________ Reflecting layer is Al 400.ANG. thick n.sub.1 = 2.1 n.sub.2 = 1.5 n.sub.me = 3.72 + i3.88 and 3.62 + i3.83 TABLE 6__________________________________________________________________________MO = 200.ANG. 250.ANG. 300.ANG. 350.ANG.x(t) x(b) R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat__________________________________________________________________________50 100 31 6.2 -1 0.342 32 6.0 -14 0.330 34 5.7 -22 0.308 35 5.4 -28 0.283 200 26 6.7 -14 0.332 29 6.3 -25 0.309 32 5.8 -32 0.282 35 5.4 -37 0.256 300 24 7.0 -26 0.306 28 6.4 -35 0.280 32 5.9 -40 0.253 35 5.3 -43 0.230 400 22 7.2 -36 0.270 27 6.5 -43 0.247 32 5.2 -47 0.224 35 5.3 -49 0.204150 100 28 6.4 -4 0.341 30 6.2 -16 0.327 32 5.9 -25 0.304 33 5.6 -30 0.279 200 24 6.9 -17 0.324 27 6.5 -28 0.301 30 6.0 -34 0.275 33 5.6 -39 0.250 300 21 7.2 -29 0.293 26 6.6 -38 0.269 30 6.1 -43 0.244 33 5.5 -46 0.223 400 20 7.4 -40 0.253 25 6.7 -46 0.233 30 6.1 -50 0.213 33 5.4 -52 0.196250 100 25 6.7 -5 0.337 27 6.5 -18 0.322 29 6.2 -26 0.299 31 5.9 -32 0.275 200 21 7.2 -19 0.314 25 6.8 -30 0.292 28 6.3 -36 0.268 32 5.8 -41 0.245 300 19 7.5 -31 0.277 24 6.9 -40 0.257 27 6.3 -45 0.235 31 5.8 -47 0.216 400 17 7.6 -43 0.234 23 7.0 -49 0.219 27 6.3 -52 0.202 31 5.7 -53 0.188350 100 22 7.0 -6 0.330 24 6.8 -19 0.316 26 6.5 -28 0.294 28 6.2 -33 0.272 200 18 7.5 -20 0.302 22 7.1 -31 0.282 26 6.6 -38 0.260 28 6.1 -42 0.239 300 16 7.8 -33 0.261 21 7.2 -42 0.244 25 6.6 -46 0.226 28 6.0 -49 0.210 400 15 7.9 -45 0.215 20 7.3 -51 0.205 24 6.6 -54 0.293 28 6.0 -55 0.281450 100 19 7.4 -6 0.320 21 7.2 -19 0.308 23 6.9 -28 0.288 25 6.5 -34 0.267 200 15 7.8 -20 0.288 19 7.4 -31 0.273 22 6.9 -38 0.254 24 6.4 -42 0.235 300 13 8.1 -33 0.245 18 7.5 -42 0.234 21 6.9 -47 0.219 24 6.4 -49 0.205 400 12 8.2 -46 0.198 17 7.6 -52 0.294 21 6.9 -54 0.286 25 6.3 -55 0.177550 100 16 7.6 -3 0.309 18 7.5 -17 0.301 20 7.2 -26 0.284 21 6.8 -32 0.265 200 13 8.1 -18 0.275 16 7.7 -30 0.265 19 7.2 -37 0.249 21 6.7 -42 0.233 300 11 8.3 -31 0.232 15 7.8 -41 0.226 18 7.2 -46 0.216 21 6.7 -48 0.204 400 09 8.5 -44 0.187 14 7.9 -51 0.187 18 7.2 -54 0.183 22 6.6 -55 0.176650 100 15 7.8 1 0.299 16 7.7 -13 0.295 17 7.4 -23 0.262 29 7.0 -30 0.266 200 11 8.3 -13 0.266 14 7.9 -26 0.261 16 7.5 -34 0.250 12 7.0 -39 0.236 300 09 8.5 -26 0.226 12 8.0 -37 0.225 16 7.5 -43 0.218 19 6.9 -46 0.208 400 07 8.7 -40 0.183 12 8.1 -47 0.188 16 7.5 -51 0.186 19 6.8 -52 0.181750 100 14 7.9 7 0.293 15 7.8 -8 0.294 16 7.5 -19 0.285 18 7.2 -25 0.271 200 10 8.4 -6 0.265 12 8.0 -21 0.265 15 7.6 -29 0.256 17 7.1 -34 0.244 300 08 8.6 -19 0.229 12 8.2 -32 0.232 14 7.6 -38 0.226 17 7.1 -42 0.218 400 06 8.8 -32 0.190 10 8.3 -42 0.198 14 7.6 -46 0.197 17 7.0 -48 0.193850 100 15 7.8 12 0.292 15 7.8 -3 0.299 16 7.5 -13 0.293 18 7.2 -20 0.281 200 11 8.3 1 0.272 12 8.0 -14 0.275 15 7.6 -24 0.268 17 7.1 -29 0.257 300 08 8.6 -12 0.241 11 8.2 -25 0.246 14 7.7 -33 0.242 17 7.1 -37 0.233 400 06 8.8 -22 0.207 10 8.3 -35 0.216 14 7.7 -41 0.215 17 7.0 -43 0.209950 100 16 7.6 16 0.297 26 7.6 2 0.308 17 7.4 -9 0.304 19 7.0 -16 0.293 200 12 8.1 6 0.283 24 7.9 -9 0.290 16 7.5 -19 0.284 18 7.0 -25 0.272 300 09 8.5 -4 0.260 12 8.1 -19 0.266 15 7.6 -27 0.261 18 7.0 -32 0.250 400 08 8.7 -14 0.231 11 8.2 -28 0.239 14 7.6 -35 0.236 18 6.9 -38 0.2281050 100 19 7.4 19 0.305 19 7.3 5 0.319 20 7.1 -6 0.316 21 6.8 -13 0.305 200 15 7.9 9 0.299 16 7.7 -6 0.306 18 7.3 -15 0.299 20 6.8 -22 0.286 300 12 8.2 -1 0.282 14 7.9 -15 0.286 17 7.4 -24 0.279 20 6.8 -29 0.266 400 10 8.5 -10 0.258 13 8.0 -24 0.263 16 7.4 -31 0.257 20 6.7 -35 0.2451150 100 22 7.0 19 0.314 22 7.0 6 0.328 23 6.8 -5 0.325 24 6.5 -12 0.313 200 IS 7.6 9 0.314 19 7.3 -4 0.320 21 7.0 -14 0.312 23 6.5 -20 0.296 300 14 7.9 0 0.302 17 7.6 -13 0.304 20 7.1 -22 0.293 23 6.5 -27 0.277 400 12 8.2 -9 0.282 16 7.7 -22 0.283 19 7.1 -29 0.273 23 6.5 -33 0.257__________________________________________________________________________ Reflecting layer is Cu 400.ANG. thick n.sub.1 = n.sub.2 = 2.1 n.sub.me = 3.72 + i3.88 and 3.62 + i3.83 TABLE 7__________________________________________________________________________MO = 150.ANG. 200.ANG. 250.ANG. 300.ANG.x(t) x(b) R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat__________________________________________________________________________50 0 41 4.9 30 0.273 37 5.4 13 0.321 36 5.6 0 0.333 36 5.5 -10 0.325 100 31 6.1 16 0.326 32 6.2 -2 0.342 32 6.0 -14 0.330 34 5.7 -22 0.308 200 24 6.9 69 0.338 26 6.7 -14 0.332 29 6.3 -25 0.309 32 5.8 -32 0.282 300 29 7.5 -10 0.321 24 7.0 -26 0.306 28 6.4 -35 0.280 32 5.9 -40 0.253150 0 39 5.2 28 0.282 35 5.6 12 0.327 34 5.8 -2 0.336 34 5.7 -12 0.325 100 28 6.3 14 0.329 28 6.4 -4 0.341 30 6.2 -16 0.327 32 5.9 -25 0.304 200 22 7.2 0 0.332 24 6.9 -17 0.324 27 6.6 -28 0.302 30 6.0 -34 0.275 300 17 7.7 -13 0.307 21 7.2 -29 0.293 26 6.6 -38 0.269 30 6.2 -43 0.244250 0 36 5.5 28 0.269 32 5.9 10 0.330 31 6.1 -3 0.337 31 6.0 -14 0.325 100 25 6.7 13 0.328 25 6.7 -5 0.337 27 6.5 -18 0.322 29 6.2 -26 0.299 200 19 7.5 -2 0.322 21 7.2 -19 0.314 25 6.8 -30 0.292 28 6.3 -36 0.268 300 14 8.0 -16 0.289 19 7.5 -31 0.277 24 6.9 -40 0.257 27 6.3 -45 0.235350 0 32 5.8 27 0.293 29 6.3 10 0.331 28 6.4 -4 0.336 28 6.3 -15 0.323 100 22 7.0 12 0.322 22 7.0 -6 0.330 24 6.8 -19 0.316 26 6.5 -28 0.294 200 16 7.8 -8 0.307 IS 7.5 -20 0.302 22 7.1 -31 0.282 25 6.6 -38 0.260 300 12 8.3 -17 0.268 16 7.8 -33 0.261 21 7.2 -42 0.244 25 6.6 -46 0.226450 0 29 6.1 28 0.291 25 6.6 20 0.328 24 6.7 -4 0.332 25 6.7 -15 0.319 100 19 7.3 13 0.312 19 7.4 -6 0.320 22 7.2 -19 0.308 23 6.9 -28 0.288 200 13 8.1 -1 0.289 15 7.8 -20 0.288 19 7.4 -31 0.273 22 6.9 -38 0.254 300 09 8.5 -16 0.246 13 8.1 -33 0.245 18 7.5 -42 0.234 21 6.9 -47 0.219550 0 27 6.4 30 0.284 23 6.9 12 0.320 21 7.0 -2 0.325 22 7.0 -13 0.315 100 17 7.5 16 0.296 16 7.6 -3 0.309 18 7.5 -17 0.301 20 7.2 -26 0.284 200 11 8.3 3 0.271 13 8.1 -18 0.275 16 7.7 -30 0.265 19 7.2 -37 0.249 300 07 8.7 -12 0.226 11 8.3 -31 0.232 15 7.8 -41 0.226 18 7.2 -46 0.216650 0 25 6.5 33 0.273 22 7.1 16 0.311 19 7.2 1 0.319 19 7.2 -10 0.311 100 IS 7.7 22 0.281 15 7.8 1 0.299 16 7.7 -13 0.295 17 7.4 -23 0.282 200 09 8.4 9 0.255 11 8.3 -13 0.266 14 7.9 -26 0.261 26 7.5 -34 0.250 300 06 8.9 -4 0.214 09 8.5 -26 0.226 12 8.0 -37 0.225 16 7.5 -43 0.218750 0 24 6.6 37 0.260 20 7.1 20 0.301 18 7.3 6 0.314 18 7.3 -6 0.310 100 15 7.7 27 0.269 14 7.9 7 0.293 15 7.8 -8 0.294 16 7.5 -19 0.285 200 09 8.4 17 0.247 10 8.4 -6 0.265 12 8.0 -21 0.265 15 7.6 -29 0.256 300 06 8.9 6 0.221 08 8.6 -19 0.229 11 8.2 -32 0.232 14 7.6 -38 0.226850 0 26 6.5 40 0.249 21 7.1 24 0.294 19 7.3 10 0.312 19 7.3 -1 0.313 100 16 7.6 31 0.262 15 7.8 12 0.292 15 7.8 -3 0.299 16 7.5 -13 0.293 200 11 8.3 23 0.247 11 8.3 1 0.272 22 8.0 -14 0.275 15 7.6 -24 0.268 300 07 8.8 15 0.218 08 8.6 -11 0.241 11 8.2 -25 0.246 14 7.7 -33 0.242950 0 28 6.2 43 0.241 23 6.9 28 0.291 22 7.1 14 0.314 20 7.1 3 0.318 100 19 7.3 35 0.261 16 7.6 16 0.297 26 7.6 2 0.308 17 7.4 -9 0.304 200 13 8.1 27 0.255 12 8.2 6 0.283 14 7.9 -9 0.290 16 7.5 -19 0.284 300 08 8.6 20 0.234 09 8.5 -4 0.260 22 8.1 -29 0.266 25 7.6 -27 0.2621050 0 31 5.9 44 0.237 26 6.6 29 0.291 23 6.8 16 0.317 23 6.8 6 0.325 100 22 7.0 36 0.265 19 7.4 19 0.305 19 7.3 5 0.319 20 7.1 -6 0.316 200 15 7.8 29 0.267 15 7.9 9 0.299 16 7.7 -6 0.306 18 7.3 -15 0.299 300 11 8.3 22 0.254 12 8.2 -1 0.282 14 7.9 -15 0.286 17 7.4 -24 0.2791150 0 34 5.6 44 0.235 29 6.2 30 0.292 27 6.5 17 0.321 26 6.5 6 0.330 100 25 6.7 36 0.271 22 7.0 19 0.314 22 7.0 6 0.328 23 6.8 -5 0.325 200 18 7.5 29 0.282 18 7.6 9 0.314 19 7.3 -4 0.320 21 7.0 -14 0.322 300 14 8.0 21 0.276 14 7.9 0 0.302 17 7.6 -13 0.304 20 7.1 -22 0.293__________________________________________________________________________ Reflecting layer is Cu 400.ANG. thick n.sub.1 = n.sub.2 = 2.1 n.sub.me = 3.72 + i3.88 and 3.62 + i3.83 TABLE 8__________________________________________________________________________MO = 200.ANG. 250.ANG. 300.ANG. 350.ANG.x(t) x(b) R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat__________________________________________________________________________50 100 31 6.1 0 0.342 32 6.0 -12 0.332 34 5.7 -21 0.311 36 5.4 -27 0.286 200 27 6.6 -11 0.338 30 6.3 -22 0.317 33 5.8 -30 0.290 35 5.4 -35 0.264 300 25 6.9 -20 0.322 29 6.4 -30 0.296 32 5.9 -36 0.268 35 5.4 -40 0.243 400 23 7.1 -28 0.300 28 6.5 -37 0.274 32 5.9 -42 0.248 35 5.3 -45 0.224150 100 29 6.4 -2 0.342 30 6.2 -15 0.330 32 5.9 -23 0.307 34 5.6 -30 0.282 200 25 6.8 -13 0.332 28 6.5 -25 0.310 31 6.0 -32 0.284 33 5.6 -37 0.258 300 22 7.1 -23 0.311 27 6.6 -33 0.286 30 6.1 -39 0.260 33 5.6 -42 0.237 400 21 7.3 -31 0.286 26 6.7 -40 0.262 30 6.1 -44 0.238 33 5.5 -47 0.217250 100 26 6.7 -4 0.339 27 6.5 -16 0.326 29 6.2 -25 0.303 31 5.9 -31 0.279 200 22 7.1 -15 0.323 25 6.7 -27 0.302 28 6.3 -34 0.277 31 5.9 -39 0.253 300 20 7.4 -25 0.298 24 6.9 -35 0.276 28 6.3 -41 0.252 31 5.8 -44 0.230 400 18 7.6 -34 0.269 23 7.0 -42 0.249 27 6.3 -47 0.228 31 5.8 -49 0.210350 100 23 7.0 -4 0.333 24 6.8 -17 0.320 26 6.5 -26 0.298 28 6.2 -32 0.275 200 19 7.4 -16 0.312 22 7.1 -28 0.293 25 6.6 -35 0.270 28 6.1 -40 0.248 300 17 7.7 -27 0.283 21 7.2 -37 0.264 25 6.6 -42 0.244 28 6.1 -46 0.224 400 16 7.9 -36 0.252 20 7.3 -44 0.236 24 6.6 -48 0.219 28 6.1 -50 0.203450 100 20 7.3 -4 0.323 21 7.2 -17 0.312 23 6.9 -26 0.292 25 6.5 -33 0.271 200 16 7.8 -16 0.299 19 7.4 -28 0.283 22 6.9 -36 0.264 24 6.5 -40 0.244 300 14 8.0 -27 0.268 18 7.5 -37 0.254 21 7.0 -43 0.237 24 6.4 -46 0.220 400 13 8.2 -36 0.236 17 7.6 -44 0.225 21 7.0 -49 0.212 24 6.4 -52 0.199550 100 17 7.6 -2 0.312 18 7.5 -16 0.304 20 7.2 -25 0.288 21 6.8 -31 0.268 200 13 8.0 -14 0.286 16 7.7 -26 0.275 19 7.2 -34 0.259 21 6.8 -39 0.242 300 11 8.3 -24 0.255 15 7.8 -35 0.246 18 7.3 -42 0.233 21 6.7 -45 0.218 400 10 8.4 -34 0.223 14 7.9 -43 0.218 18 7.3 -48 0.208 21 6.7 -50 0.198650 100 15 7.8 3 0.302 16 7.7 -12 0.299 17 7.4 -22 0.286 19 7.0 -29 0.269 200 12 8.2 -9 0.277 14 7.9 -23 0.271 16 7.5 -31 0.259 19 7.0 -36 0.244 300 10 8.5 -19 0.247 13 8.0 -32 0.244 16 7.5 -39 0.234 19 7.0 -42 0.222 400 08 8.6 -29 0.217 12 8.1 -40 0.217 16 7.5 -45 0.211 19 6.9 -47 0.202750 100 14 7.9 8 0.295 15 7.8 -7 0.297 16 7.5 -17 0.288 18 7.2 -24 0.274 200 11 8.3 -3 0.274 13 8.0 -17 0.274 15 7.6 -26 0.264 17 7.2 -32 0.251 300 09 8.6 -12 0.248 12 8.2 -26 0.249 14 7.7 -34 0.241 17 7.1 -38 0.231 400 07 8.7 -21 0.221 11 8.2 -34 0.225 14 7.7 -40 0.220 17 7.1 -43 0.212850 100 15 7.8 14 0.294 15 7.7 -1 0.301 16 7.5 -12 0.296 18 7.2 -19 0.284 200 12 8.2 4 0.278 13 8.0 -11 0.282 15 7.6 -21 0.276 17 7.2 -27 0.264 300 09 8.5 -5 0.257 12 8.2 -20 0.261 14 7.7 -28 0.255 17 7.1 -33 0.245 400 08 8.7 -13 0.234 11 8.3 -27 0.240 14 7.7 -34 0.236 17 7.1 -38 0.228950 100 17 7.6 18 0.298 17 7.6 3 0.310 18 7.4 -8 0.307 19 7.0 -15 0.296 200 13 8.1 9 0.289 14 7.9 -6 0.296 16 7.5 -16 0.290 18 7.1 -23 0.278 300 11 8.4 1 0.273 13 8.0 -14 0.279 15 7.6 -23 0.273 18 7.0 -29 0.261 400 09 8.6 -6 0.255 12 8.1 -21 0.261 15 7.6 -29 0.256 18 7.0 -34 0.2461050 100 20 7.3 20 0.305 19 7.3 6 0.320 20 7.1 -5 0.318 21 6.8 -12 0.307 200 16 7.8 12 0.303 17 7.6 -3 0.311 19 7.3 -13 0.305 21 6.8 -19 0.292 300 13 8.1 4 0.292 15 7.8 -10 0.297 18 7.3 -20 0.290 20 6.8 -25 0.277 400 11 8.3 -2 0.278 14 7.9 -17 0.282 17 7.4 -25 0.275 20 6.8 -30 0.2621150 100 23 7.0 20 0.313 22 7.0 7 0.329 23 6.8 -4 0.327 24 6.5 -11 0.315 200 19 7.5 12 0.316 20 7.3 -2 0.324 22 7.0 -11 0.317 24 6.5 -18 0.302 300 16 7.8 5 0.310 18 7.5 -9 0.314 20 7.1 -18 0.304 23 6.5 -24 0.287 400 14 8.1 -1 0.299 17 7.6 -15 0.301 20 7.1 -24 0.290 23 6.5 -28 0.273__________________________________________________________________________ Reflecting layer is Cu 400.ANG. thick n.sub.1 = 2.1 n.sub.2 = 1.5 n.sub.me = 3.72 + i3.88 and 3.62 + i3.83 TABLE 9______________________________________M x(t) MO x(b) R .vertline.K.vertline. .multidot. 10.sup.3 .phi. Vsat______________________________________200 850 200 100 22 6.5 +2 0.303200 750 250 100 22 6.4 -2 0.303300 550 200 200 20 6.9 -6 0.311300 750 250 100 22 6.6 +1 0.312300 850 250 100 22 6.6 +5 0.310400 550 200 200 20 7.0 -5 0.313400 650 200 200 18 7.2 -2 0.307400 750 250 100 22 6.7 +2 0.314400 850 250 100 22 6.7 +5 0.312400 850 300 100 22 6.8 -5 0.3122000 450 200 200 23 6.7 -6 0.3212000 550 200 200 20 7.0 -5 0.3142000 750 250 100 22 6.7 +2 0.3152000 850 250 100 18 7.3 -7 0.304______________________________________ Reflecting layer is Al n.sub.1 = n.sub.2 = 2.0 n.sub.me = 3.72 + i3.88 and 3.62 + i3.83

APPENDIX A

In this program, which is in Fortran, N.sub.1 -N.sub.6 represent the indices of refraction of the following:

N.sub.1 : the atmosphere (air) N.sub.2 : the metal reflecting layer N.sub.3 : the second dielectric layer N.sub.4 : the magneto-optic layer N.sub.5 : the first dielectric layer N.sub.6 : the substrate.

The thickness and refractive index of the metal reflecting layer is input as a single value. The program calculates the characteristics of the quadrilayer structure for a range of thicknesses of the magneto-optic layer, the first dielectric layer and the second dielectric layer. The subscript "1" generally represents the minimum thickness, the subscript "2" represents the maximum thickness, and the subscript "3" represents the incremental steps within each range.

K.sub.1, K.sub.2 and K.sub.3 refer to the thickness of the magneto-optic layer L.sub.1, L.sub.2 and L.sub.3 refer to the thickness of the second dielectric layer M.sub.1, M.sub.2 and M.sub.3 refer to the thickness of the first dielectric layer.

The appropriate values for these layers are input at the places indicated in the program. All thicknesses are expressed in Angstrom units.

Lambda represents the wavelength of the incident polarized light.

The characteristics to be calculated are represented in the program as follows:

R=the reflectivity of the structure RY=K (the magneto-optic figure of merit) =.THETA..sqroot.R, where .THETA. is the magneto-optic Kerr rotation RYP=Vsat=.sqroot.R.multidot.100.vertline.K.vertline..multidot.Cos .phi. PHIE=.phi. (the phase shift) __________________________________________________________________________ IMPLICIT REAL*8(A-H,O-Z) REAL*8 LAMDA, KD, IO, KERR COMPLEX*16 KO,E4(2),N1,N2,N3,N4(2),N5,N6,A(20)C*************************************************************** INVERT=1 N1=(1.0,0.)C********* ALUMINUM ********C N2=(2.70,8.30)C WRITE(6,201)201 FORMAT(1X,`ALUMINUM REFLECTING LAYER`/)C********* COPPER ********** N2=(0.26,5.26) WRITE(6,202)202 FORMAT(1X,`COPPER REFLECTING LAYER`/)C********* GOLD *************C N2=(0.07,5.00)C WRITE(6,203)203 FORMAT(1X,`GOLD REFLECTING LAYER`/)C********* SILVER *********C N2=(0.27,5.79)C WRITE(6,204)204 FORMAT(1X,`SILVER REFLECTING LAYER`/)C******************************* WRITE(6,301)301 FORMAT(/5X,`ENTER N AND K FOR TOP DIELECTRIC LAYER`) READ(5,*)AUX1,AUX2 N3=AUX1*(1.,0.)+AUX2*(0.,1.) WRITE(6,303)303 FORMAT(/5X,`ENTER N AND K FOR BOTTOM DIELECTRIC LAYER`) READ(5,*)AUX8,AUX9 N5=AUX8*(1.,0.)+AUX9*(0.,1.) E4(1)=(-1.4,28.3) E4(2)=(0.57,-0.12) N4(1)=CDSQRT(E4(1)+(0.,1.)*E4(2)) N4(2)=CDSQRT(E4(1)-(0.,1.)*E4(2)) WRITE(6,302)302 FORMAT(/5X,`ENTER N AND K FOR SUBSTRATE`) READ(5,*)AUX3,AUX4 N6*AUX3*(1.,0.)+AUX4*(1.,0.) SUB=REAL(N6) PLF=(4.*SUB)/((1.+SUB)**2) LAMDA=8300.C ETA=0.5C PO=1.E-3C BW=1.E7C IO=12.5E-12C KD=.02C EC=1.6E-19 KO=(0.,4.)*3.1415926536/LAMDA***************************************************************** WRITE(*,9) SUB.PLF9 FORMAT(1X,F7.4,3X,F7.4) WRITE(*,10)10 FORMAT(`ENTER REFLECTING LAYER``S THICKNESS: `,$) READ(*,*) TR WRITE(*,30)30 FORMAT(/,`THICKNESS VARIES BETWEEN X1 AND X2 IN STEPS OF X3`,/)40 FORMAT(`ENTER X1, X2 AND X3 FOR THE`,A19,$)20 WRITE(*,40)`MAGNETIC LAYER:` CALL SUB1(K1,K2,K3) IF(K1.LE.1)GOTO 20 WRITE(*,40)`X-TOP LAYER:` CALL SUB1(L1,L2,L3) WRITE(*,40) `X-BOTTOM LAYER:` CALL SUB1 (M1,M2,M3)C*************************************************************** A(1)=(N2-N1)/(N2+N1)*CDEXP(KO*N2*TR) A(2)=(N3-N2)/(N3+N2) A(3)=(A(1)+A(2))/(1.+A(1)*A(2)) A(4)=(N4(1)-N3)/(N4(1)+N3) A(5)=(N4(2)-N3)/(N4(2)+N3) A(6)=(N5-N4(1))/(N5+N4(1)) A(7)=(N5-N4(2))/(N5+N4(2)) A(8)=(N6-N5)/(N6+N5)C*************************************************************** OPEN(UNIT=20,FILE=`E:\FORPG\MPR1.PRN`) WRITE(20,99)99 FORMAT(1X,`INPUT DATA`/) WRITE(20,96) N696 FORMAT(1X,`N(SUBSTR) = `,2(F5.2,1X)) WRITE(20,100) TR,N2,N3,N4,N5100 FORMAT(1X,F5.0,2X,8(F5.2.1X)/) WRITE(20,97)97 FORMAT(1X,`X-TOP`,2X,`M-O`,2X,`X- BOT,4X,`RX2`,7X,`RY`,10X,`PHI`,5X+ ,8X,`R*RY*C(PHI)`)C*************************************************************** DO 140 K=K1,K2,K3 TF=FLOAT(K-1) A(9)=CDEXP(KO*N4(1)*TF) A(10)=CDEXP(KO*N4(2)*TF) DO 140 L=L1,L2,L3 TI=FLOAT(L-1) A(11)=A(3)*CDEXP(KO*N3*TI) A(12)=(A(4)+A(11))/(1.+A(4)*A(11))*A(9) A(13)=(A(5)+A(11))/(1.+A(5)*A(11))*A(10) A(14)=(A(6)+A(12))/(1.+A(6)*A(12)) A(15)=(A(7)+A(13))/(1.+A(7)*A(13)) DO 140 M=M1,M2,M3 TC=FLOAT(M-1) A(16)=CDEXP(KO*N5*TC) A(17)=A(14)*A(16) A(18)=A(15)*A(16) A(19)=(A(8)+A(17))/(1.+A(8)*A(17)) A(20)=(A(8)+A(18))/(1.+A(8)*A(18)) RX2=.25*CDABS((A(19)+A(20))**2) RX2=RX2*PLF*PLF RY2=.25*CDABS((A(19)-A(20))**2) RY2=RY2*PLF*PLF PHI=1.5708+(DIMAG(DCLOG((1.+A(19)/A(20))/(1.- A(19)/A(20)))))C***************************************************************C RR=DSQRT(4.*RX2*RY2*DCOS(PHI)**2+(RX2-RY2)**2)C KERR=90.*DACOS((RX2-RY2)/RR)/3.1415926536C ELL=180.*DATAN(DSQRT((RX2+RY2-RR)/(RX2+RY2+RR)))/3.14159 R-RX2+RY2 RY=100.*DSQRT(RY2) RYP=RY*DCOS(PHI) PHID=PHI*180./3.1415926536 RYPR=RYP*DSQRT(RX2) WRITE(20,90) TI,TF,TC,TX2,RY,PHID,RYPR90 FORMAT(1X,3(F5.0,1X),F6.4,4X,F6.4,6X,F7.2,6X,F7.4)140 CONTINUE ENDC*************************************************************** SUBROUTINE SUB1(T1,T2,T3) REAL*8 X1,X2,X3 READ(*,*) X1,X2,X3 IF(X2.LT.X1) X2=X1 IF(X3.LE.0.) X3=1. I1=IDNINT(X1+1.) I2=IDNINT(X2+1.) I3=IDNINT(X3) RETURN END__________________________________________________________________________

Claims

1. A magneto-optic storage medium for storing and retrieving data by exposure to a polarized light beam, said storage medium comprising a quadrilayer structure arranged in the following sequence and bonded to a transparent substrate:

a first dielectric layer having a thickness in the range of 250 .ANG. to 1150 .ANG. and comprising a material having a refractive index greater than 1.9;

a magneto-optic layer having a thickness in the range of 150 .ANG. to 350 .ANG.;

a second dielectric layer having a thickness in the range of 50 .ANG. to 400 .ANG. and comprising a material having a refractive index greater than 1.4; and

a metal reflecting layer having a thickness in the range of 150 .ANG. to 500 .ANG.;

the actual thickness of each of said layers within said respective ranges and the refractive index of each of said first and second dielectric layers being selected such that said storage medium exhibits a reflectivity in the range of 15% to 25% and a phase shift in the range of -12 degrees to +12 degrees in the presence of said polarized light beam.

2. The magneto-optic storage medium claimed in claim 1 wherein the second dielectric layer comprises a dielectric material selected from the group consisting of ZYA and SiO.sub.2.

3. The magneto-optic storage medium claimed in claim 1 wherein the second dielectric layer comprises a material having a thermal conductivity of less than 0.06 Joules/sec-cm-.degree.K.

4. The magneto-optic storage medium claimed in claim 1 wherein the metal reflecting layer is made of a material which comprises at least one metal selected from the group consisting of Al, Cu, Ag and Au.

5. The magneto-optic storage medium claimed in claim 1 wherein the transparent substrate is bonded to the first dielectric layer.

6. The magneto-optic storage medium claimed in claim 1 additionally comprising a protective layer bonded to the quadrilayer structure on the side thereof opposite to the transparent substrate.

7. The magneto-optic storage medium claimed in claim 1 wherein at least one of said layers is sputter deposited.

8. The magneto-optic storage medium claimed in claim 4 wherein the metal reflecting layer is made of a material which comprises Al alloyed with Ti or Ta.