Patent Application
20080080587
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:
A description is given, with reference to the accompanying drawings, of embodiments of the present invention.
In this specification, the term “recording magnetic field” includes not only a magnetic field serving for recording generated around the magnetic gap part of a recording element but also a magnetic field generated in the area other than around the magnetic gap part, or a so-called leakage magnetic field, unless otherwise noted.
Referring to
The measurement apparatus 10 operates in accordance with a program stored in the memory 24 or a command input from the input part 23, and measures the recording magnetic field strength distribution of the magnetic head 11. The program causes the measurement apparatus 10 to execute the steps of a flowchart shown in
Referring to
The suspension 31 has its base fixed to the positioning mechanism 14 of the measurement apparatus 10. The head slider 34 is caused to fly over the measurement medium 50 by the air bearing generated between the medium-opposing surface 34a of the head slider 34 and the surface of the measurement medium 50 by the rotation of the measurement medium 50.
As shown in
The recording element 36 includes a lower magnetic pole 36a and an upper magnetic pole 36b each formed of a soft magnetic material such as a FeCo alloy or a NiFe alloy and a recording gap part 37 formed of an alumina film 41 sandwiched between the lower magnetic pole 36a and the upper magnetic pole 36b. The lower magnetic pole 36a and the upper magnetic pole 36b are magnetically connected through a yoke of a soft magnetic material disposed in the depth direction from the medium-opposing surface 34a. Further, a recording coil 43 (
Referring back to
The positioning mechanisms 14 and 16 support the magnetic head 11 and the reproduction head 60, respectively. Further, the positioning mechanisms 14 and 16 control the radial positions of the magnetic head 11 and the reproduction head 60 based on instructions from the positioning control parts 13 and 63, respectively.
The positions of the magnetic head 11 and the reproduction head 60 may be controlled by recording tacking servo information on the measurement medium 50 in advance. The tracking servo information reproduced by the magnetic head 11 and the reproduction head 60 is fed to the control operation part 22 through the recording and reproduction control part 19. The control operation part 22 feeds position error correction signals for the heads 11 and 60 to the positioning control parts 13 and 63 based on the tracking servo information. The positioning control parts 13 and 63 control the positions of the magnetic head 11 and the reproduction head 60, respectively, based on the position error correction signals. As a result, the positions of the magnetic head 11 and the reproduction head 60 can be controlled with more accuracy, so that track positioning can be performed with high position accuracy. Consequently, the reproduction output of a magnetic track with better position accuracy is obtained, thus resulting in better position accuracy of the magnetic field strength distribution of the magnetic head 11.
Although not graphically illustrated, the laser light emission part 16 includes a light source such as a semiconductor laser, a condenser lens, a positioning mechanism for determining an exposure position, and a focus servo mechanism. The laser light emission part 16 emits laser light into a spot on the measurement medium 50 based on a laser exposure position control signal and a laser power control signal provided from the emission control part 15.
The emission control part 15 includes an exposure position control part 15a and a laser power control part 15b (
As shown in
The recording and reproduction part 19 converts a recording signal of a predetermined recording frequency into a recording current and supplies the recording current to the recording coil 43 (
The reproduction output measurement part 21 performs A/D conversion on the reproduced signal by detecting its peak values, and feeds the A/D-converted reproduced signal to the control operation part 22 as digital data (reproduction output data).
The control operation part 22 is, for example, a personal computer. The control operation part 22 records the reproduction output data, laser light exposure position information corresponding to the reproduction output data, and head position information in the memory 24. Further, the control operation part 22 performs an operation to convert the reproduction output data into magnetic field strength. Further, the control operation part 22 records the magnetic field strength of the magnetic head 11 in the memory 24 such as a RAM, a hard disk unit, or an optical disk unit, and displays the magnetic field strength of the magnetic head 11 on the display part 25.
In a below-described second embodiment, the control operation part 22 has the function of converting a temperature Ta at which reproduction output appears into the magnetic field strength of the magnetic head 11 based on the relationship between the coercive force of the measurement medium 50 and temperature (shown in
Next, a description is given of a method of measuring the magnetic field strength distribution of the magnetic head 11 using the measurement apparatus 10. First, a description is given of measurement principles.
Referring to
A magnetic recording medium having a recording layer whose magnetocrystalline easy axis is oriented along the direction of one of the recording magnetic fields of the magnetic head 11 which one is an object of measurement (for example, a direction parallel to, perpendicular to, or inclined to the substrate surface) is selected as the measurement medium 50.
For example, if the direction of the recording magnetic field to be subjected to measurement is parallel to the substrate surface, a so-called longitudinal (in-plane) magnetic recording medium, or a magnetic recording medium having the recording layer 53 whose magnetocrystalline easy axis is substantially parallel to the substrate surface, is employed. If the direction of the recording magnetic field to be subjected to measurement is perpendicular to the substrate surface, a magnetic recording medium having the recording layer 53 whose magnetocrystalline easy axis is substantially perpendicular to the substrate surface is employed. Further, if the direction of the recording magnetic field to be subjected to measurement is inclined to the substrate surface, a so-called oblique orientation magnetic recording medium, or a magnetic recording medium having the recording layer 53 whose magnetocrystalline easy axis has an angle greater than 0° and less than 90° to the substrate surface, is employed. In the first embodiment, the magnetic field strength of the magnetic head 11 in a direction parallel to the substrate surface (so-called horizontal magnetic field strength) is measured, and a longitudinal magnetic recording medium is employed as the measurement medium 50.
The substrate 51 is not limited in particular as long as the substrate 51 transmits laser light. Preferably, the substrate 51 is a transparent substrate such as a glass substrate or a resin substrate.
Linear unevenness, or so-called texture, may be formed along a recording direction on the surface of the substrate 51. Further, an orientation control film (not graphically illustrated) such as a NiP film may be provided on the surface of the substrate 51. In this case, the texture may be formed along a recording direction on either the surface of the substrate 51 or the surface of the orientation control film. The formation of the texture causes the magnetocrystalline easy axis of the recording layer 53 to be oriented in the recording direction, so that the recording layer 53 having uniaxial anisotropy is formed. As a result, fluctuation in the magnetocrystalline easy axis of the recording layer 53 is reduced, so that it is possible to measure magnetic field strength distribution with higher resolution than in the case of forming no texture. In the case of providing the orientation control film, laser light is emitted onto the orientation control film, and the recording layer 53 is heated by heat conduction through the underlayer 52.
The underlayer 52 is formed of, for example, Cr or a Cr alloy such as CrMo or CrV. As a result, the underlayer 52 is caused to orient the magnetocrystalline easy axis of the recording layer 53 formed of a Co-based alloy parallel to the substrate surface.
A known ferromagnetic material such as a Co-based alloy may be employed for the recording layer 53. Preferably, however, the recording layer 53 is formed of a ferromagnetic material containing Co and Pt, which has large magnetic anisotropy, such as CoPt, CoCrPt, or CoCrPt-M, where M is one selected from the group consisting of B, Mo, Nb, Ta, W, and Cu. As a result, the coercive force can be increased by the addition of Pt to the ferromagnetic material of the recording layer 53, so that a measurement medium having a coercive force higher than the maximum recording magnetic field strength of the magnetic head 11 at room temperature can be obtained easily as described next. Further, even if the crystal grains of the recording layer 53 are fine, for example, 10 nm or less in average grain size, the thermal stability of residual magnetization is good. Accordingly, it is possible to suppress reduction in residual magnetization during measurement.
Further, the recording layer 53 may have two magnetic layers each formed of a ferromagnetic material and a non-magnetic coupling layer of Ru having a thickness of, for example, 0.7 nm between the magnetic layers, where the two magnetic layers are antiferromagnetically coupled to each other. The recording layer 53 having such a structure is more preferable because the thermal stability of residual magnetization is better.
The recording layer 53 may have a so-called granular structure, or a structure formed of multiple crystal grains of a ferromagnetic material and a non-magnetic material (for example, SiO2) surrounding each crystal grain. It is also preferable in this case that the ferromagnetic material be the one containing Co and Pt as described above in terms of large magnetic anisotropy and good thermal stability. In this case, it is preferable to further form an intermediate layer of Ru or a Ru alloy containing Ru as a principal component between the underlayer 52 and the recording layer 53. This makes it possible to reduce zigzag noise at high recording density, so that it is possible to measure the reproduction output of a finer area, thus increasing the position resolution of reproduction output.
A known material such as a carbon film or hydrogenated carbon may be employed for the protection film 54. Further, although not graphically illustrated, a lubricating layer may be formed on the protection film 54.
Next, a description is given of measurement principles. Referring to
Further, at the time of signal recording, laser light emitted from the laser light emission part 16 enters the measurement medium 50 from its bottom side so as to pass (be transmitted) through the substrate 51 and form a laser spot BS in the underlayer 52. The underlayer 52 and the recording layer 53 are heated so that the temperature of a fine area HA smaller in size than the laser spot BS rises to a predetermined value. As a result, the coercive force of the recording layer 53 becomes lower than that at room temperature in the fine area HA, so that the recording layer 53 in the fine area HA is magnetized with a smaller magnetic field strength.
The heated fine area HA is required to be smaller than the size of the recording element 36 in a direction in which measurement is performed. The smaller the heated fine area HA, the better. Hence, the smaller the laser spot BS in size, the better. The spot size (diameter) of the laser spot BS is preferably in the range of, for example, 0.9 μm or less. A spot size about the size of diffraction limit is preferable in particular. The spot size can be particularly small in the case of employing near-field light. The temperature of the fine area HA heated by the laser spot BS is not limited in particular, but should be determined so that no damage is caused to the measurement medium 50.
Referring to
This is because consequently, recording is performed only in the heated fine area HA and the magnetization layer 53 is not magnetized in the other area even if a recording magnetic field of the maximum recording magnetic field density Hhm is applied to the other area. The coercive force Hc of the measurement medium 50 at room temperature TRT may be lower than the maximum recording magnetic field density Hhm. In this case, the coercive force Hc at room temperature TRT needs to be such that a reproduced signal from the heated and recorded fine area HA is greater than a reproduced signal from the area other than the fine area HA.
Preferably, the ferromagnetic material of the recording layer 53 of the measurement medium 50 is selected in accordance with the maximum recording magnetic field density Hhm of the magnetic head 11. Further, since the maximum recording magnetic field density Hhm changes in accordance with the magnitude of a recording current caused to flow through the magnetic head 11, the ferromagnetic material of the recording layer 53 is selected in accordance with the change.
Then, by heating the fine area HA of the recording layer 53 (to the temperature Tch) by exposure to laser light, the coercive force of the fine area HA is reduced to Hch. At this point, when a magnetic field greater than the coercive force Hch of the heated fine area HA (the recording magnetic field H1 or the leakage magnetic field H2) is applied from the magnetic head 11, the fine area HA is magnetized. In the magnetized fine area HA, magnetization M (indicated by outline arrow M) remains even when the temperature is lowered to room temperature, and the magnetic track 53a is formed in the recording layer 53. The magnetic track 53a is substantially equal in width to the fine area HA, and is formed along a moving direction RD in which the measurement medium 50 moves. The magnetization M of the magnetic track 53a formed herein has a magnetization corresponding to the magnetic field strength applied in the heated state.
It is preferable that the coercive force Hch of the heated recording layer 53 be as low as possible, for example, 2 kOe or less. This makes it possible to detect every leakage magnetic field.
The coercive force of the recording layer 53 having the magnetic track 53a formed therein returns to Hc when the temperature returns to room temperature. Accordingly, even if the recording magnetic field H1 (the maximum recording magnetic field density Hhm) is applied near the magnetic gap part 37 in this state, the magnetization M of the magnetic track 53a is not affected thereby and remains. That is, even if a laser light exposure position is set on the upstream side in the moving direction RD of the measurement medium 50, the magnetization M of the magnetic track 53a is not affected by the recording magnetic field H1 of the magnetic gap part 37. Accordingly, the magnetic track 53a corresponding to the strength of a leakage magnetic field (or a recording magnetic field) is formed at any position on the recording layer 53 corresponding to the medium-opposing surface 34a. Therefore, it is possible to measure magnetic field strength at any position on the recording layer 53 corresponding to the medium-opposing surface 34a. It is also possible to reduce a magnetic field from the recording gap part 37 onto a measurement position by providing the magnetic head 11 with a skew angle. In this case, it is possible to perform measurement even if the coercive force Hc at room temperature TRT is smaller than the maximum recording magnetic field density Hhm.
At the time of reproducing (reading) the magnetic track 53a, the emission of laser light is stopped (OFF), and the magnetic track 53a of the recording layer 53 is read with the reproduction head 60. Then, reproduction output, for example, the peak value of a reproduced signal waveform, is measured. As a result, reproduction output corresponding to the magnitude of the magnetization M is obtained. As is described below, this reproduction output is converted into magnetic field strength, so that the magnetic field strength distribution of the magnetic head 11 is finally obtained.
A description is given, with reference to
First, in step S102, initial settings are provided. In the initial settings, the measurement medium 50 (already demagnetized) is attached to the measurement apparatus 10. The measurement medium 50 is rotated at predetermined rpm so as to cause the magnetic head 11 to be subjected to magnetic field strength distribution measurement to fly over the measurement medium 50, and positioning of the magnetic head 11 is performed. Further, a predetermined recording current to be supplied to the magnetic head 11 is determined. A desired recording current value and recording frequency are selected for the recording current. Further, the reproduction head 60 is caused to fly over the measurement medium 50, and the reproduction head 60 is positioned at a radial position at which the magnetic field strength distribution of the magnetic head 11 is obtained. Further, the laser light emission part 16 is positioned so that laser light is emitted onto a reference position, for example, the position of the magnetic gap part 37. The magnetic head 11 may erase data in the recording layer 53 of the measurement medium 50 at this point.
The skew angle of each of the magnetic head 11 and the reproduction head 60 is set at, for example, 0°. The skew angle refers to an angle that the recording element longitudinal directions of the recording element 36 of the magnetic head 11 form with the moving direction (recording direction) of the measurement medium 50 in a virtual plane parallel to the substrate surface of the measurement medium 50.
It is not always required to cause the magnetic head 11 to fly over the measurement medium 50. The magnetic head 11 may also be fixed above the measurement medium 50 at such a distance from the measurement medium 50 as to enable recording. As a result, the magnetic head 11 avoids heat conduction from the heated recording layer 53, so that the recording and reproduction characteristics of the recording element 36 and the reproduction element 38 are stabilized.
Further, the magnetic field strength distribution is obtained at a laser light exposure position Li (i=1 to n). The laser light exposure position Li is suitably selected in accordance with the purpose of measurement. For example, the laser light exposure position Li is selected along an X1 axis shown in
Next, in step S104, the laser light exposure position Li (i=1) is set (determined). The laser light exposure position Li (i=1) is determined by the exposure position control part 15a.
Next, in step S106, laser light is emitted with predetermined laser power, and in step S108, the preset recording current is supplied to the recording element 36 of the magnetic head 11, thereby performing signal recording. As a result, a recording magnetic field (leakage magnetic field) from the magnetic head 11 is applied to the laser light exposure position Li, that is, the heated fine area HA, so that the recording layer 53 is magnetized. As a result, the magnetic track 53a is formed in the recording layer 53.
Next, in step S110, the emission of laser light is stopped. In step S112, the reproduction output of the magnetic track 53a is measured with the reproduction head 60 after at least one rotation after the signal recording. Specifically, the reproduction head 60 is positioned at the radial position of the magnetic track 53a, and a signal magnetic field from the magnetic track 53a is detected. A reproduced signal obtained thereby is amplified in the recording and reproduction control part 19, and the average of the amplitude of the reproduced signal (reproduction output) is obtained by the reproduction output measurement part 21. The laser light exposure position Li and the corresponding reproduced signal are correlated as a pair of data. The amplitude values of the reproduced signal, or a so-called track profile, may be measured while changing the radial position of the reproduction head 60 little by little around the radial position of the magnetic track 53a, and its maximum value may be employed as reproduction output.
Next, in step S114, it is determined whether measurement has been performed at all of the desired laser light exposure positions Li. If measurement has not been performed at all of the desired laser light exposure positions Li (NO in step S114), in step S116, the laser light exposure position Li is replaced by the next laser light exposure position Li, and in step S117, the magnetic track 53a is erased. The magnetic track 53a is erased by AC erasure or DC erasure by the magnetic head 11. At this point, laser light may be emitted onto the magnetic track 53a (recording layer 53) so as to increase the temperature of the recording layer 53, and the magnetic track 53a may be erased with a lower magnetic field by the magnetic head 11.
Next, steps S104 through 112 are performed. If measurement has been performed at all of the laser light exposure positions Li (YES in step S114), in step S118, the reproduction output (individual reproduction outputs) is converted into magnetic field strength based on the obtained relationship between the laser light exposure positions Li and the corresponding reproduction outputs. In this step (S118), first, each laser light exposure position Li is replaced by a corresponding position on the medium-opposing surface of the magnetic head 11, the position opposing the laser light exposure position Li. As a result, the relationship between the positions on the medium-opposing surface and the reproduction outputs is determined. This relationship is the profile of the reproduction outputs corresponding to the medium-opposing surface, which is, for example, as shown in below-described
Further, in this step (S118), the reproduction output is converted into magnetic field strength in the relationship between the positions on the medium-opposing surface and the individual reproduction outputs. The recording magnetic field strength of at least one of the laser light exposure positions Li (where the reproduction output has been measured) is separately measured. This measurement is performed by, for example, a measurement method according to the second embodiment or, if applicable, the method of Patent Document 1 using an electron beam as described above as related art. Assuming that the recording magnetic field strength is proportional to the reproduction output, the reproduction output is converted into magnetic field strength based on the relationship between the separately measured recording magnetic field strength and the reproduction output of the position thereof. For example, a position on the recording layer 53 corresponding to the magnetic gap part 37 is included in the laser light exposure positions Li. Then, assuming that the recording magnetic field strength is proportional to the reproduction output, the reproduction output is converted into magnetic field strength based on the ratio of the separately measured maximum recording magnetic field strength Hhm at the magnetic gap part 37 to the peak value VP (a value after subtracting noise level) of the reproduction output obtained at the magnetic gap part 37 (=Hhm/Vp). As a result, the recording magnetic field strength distribution of the magnetic head 11 at the positions on the recording layer 53 is obtained.
According to this measurement method, the measurement medium 50, which, at room temperature, has a coercive force higher than the maximum recording magnetic field strength Hhm of the measurement-target magnetic head 11 at a predetermined recording current, is employed. Then, by heating the recording layer 53 by emitting laser light of a fine laser spot onto the measurement medium 50, the coercive force of the recording layer 53 becomes lower in the heated fine area HA than in the other area. Therefore, only the fine area HA is magnetized by a recording magnetic field (including a leakage magnetic field) from the magnetic head 11, so that a magnetic track is formed. The reproduction output is measured from the magnetic track by the reproduction head 60, and the reproduction output is converted into magnetic field strength. Thereby, it is possible to detect the magnetic field strength of the recording magnetic field. Further, by changing the laser light exposure position Li and measuring reproduction outputs corresponding to multiple laser light exposure positions, the recording magnetic field strength distribution of the magnetic head 11 can be obtained. Accordingly, the magnetic field strength distribution can be measured with a simple method.
Further, according to this measurement method, measurement is performed at different laser light exposure positions while having the magnetic head 11 fixed. Accordingly, it is possible to prevent error caused by movement of the magnetic head 11, such as position error (deviation).
According to this measurement method, the reproduction output is measured by the reproduction head 60. Alternatively, the reproduction output may be measured using the reproduction element 38 of the magnetic head 11. In this case, depending on the measurement position (that is, the laser light exposure position), it may be necessary to move the magnetic head 11 in order to measure reproduction output, but it is possible to avoid the trouble of using the reproduction head 60.
In the above-described method of measuring magnetic field strength distribution, even a process only up to the stage of obtaining the reproduction output distribution corresponding to the medium-opposing surface, that is, a process only up to the stage before conversion into magnetic strength, is included in the first embodiment of the present invention. This is because effective information on the recording magnetic field strength distribution of the magnetic head 11 can be obtained from the shape of the reproduction output profile corresponding to the medium-opposing surface. That is, for example, by comparing a magnetic field strength distribution obtained with a simulation based on the design of the magnetic head 11 with the shape of the reproduction output profile corresponding to the medium-opposing surface, it is possible to discover abnormal magnetic field leakage (sub peak), etc., that is not intended in the design of the magnetic head 11.
Further, in the above-described method of measuring magnetic field strength distribution, the skew angle of the magnetic head 11 is 0°. However, the skew angle of the magnetic head 11 is not limited to 0°, and may be ±10° or an angle greater than ±10° in absolute value.
Next, a description is given of the case where the magnetic field strength distribution of the magnetic head 11 having the structure shown in
Referring to
Further, a laser head of a 655 nm wavelength was employed as a laser light emission part. Laser light emitted from the laser head was caused to enter the measurement medium from its glass substrate side, so that a laser spot BS of 0.9 μm in diameter was formed. The laser spot BS was formed at positions (laser light exposure positions) along the X1 axis from a position of −2 μm on the upper magnetic pole 36b side to a position of approximately 8.5 μm on the reproduction element 38 side with the center of the magnetic gap part 37 serving as an origin. Further, a measurement pitch (the pitch of the laser light exposure positions) PM of 0.1 μm was employed. The X1 axis is parallel to the recording element longitudinal directions (X-axial directions), and passes through the center in the element width directions (the center O of the recording gap part 37).
The measurement method according to the example implementation is the same as the measurement method shown in the flowchart of
Referring to
Further, it is also shown that the reproduction output having a sufficient position resolution is obtained with the laser spot BS of 0.9 μm in diameter and the measurement pitch PM of 0.1 μm.
Further, it is possible to obtain the magnetic field strength distribution of the magnetic head 11 by converting the reproduction output into magnetic field strength based on the ratio of the separately measured maximum recording magnetic field strength Hhm at the magnetic gap part 37 to the difference (0.16 mV) between the maximum value VP (0.52 mV) of the reproduction output at the recording gap part 37 (around where the distance is zero) and the noise level (0.36 mV).
Further, the position of the magnetic sensing part of a reproduction element may be additionally measured in the method of measuring the magnetic field strength distribution of a magnetic head according to the first embodiment. In this measurement, the measurement apparatus 10 shown in
Referring to
Next, in step S124, laser light of the reproduction laser power Qk (k=1) is emitted onto the laser light exposure position Li by the laser light emission part 16. Next, in step S126, the reproduction output of the track (formed in step S108 of
Next, in step S128, the emission of laser light is stopped (OFF). In step S130, it is determined whether measurement has been performed with respect to all the desired levels of the reproduction laser power Qk. If measurement has not been performed with respect to all the desired levels of the reproduction laser power Qk (NO in step S130), in step S132, the laser power Qk is replaced by the next laser power Qk, and steps S122 through S132 are performed.
If measurement has been performed with respect to all the desired levels of the reproduction laser power Qk (k=1, YES in step S130), the operation proceeds to step S114 of
Next, as shown in the flowchart of
It is inferred that these principles of measurement are as follows. Referring to
Referring to
This measurement of the position of the magnetic sensing part (magnetoresistive film 39) of the reproduction element 38 can be magnetically performed, and moreover is simple. The method of measuring the position of the magnetic sensing part (magnetoresistive film 39) of the reproduction element 38 can also be applied in the below-described case where the magnetic head is a perpendicular recording magnetic head.
The measurement of the position of the magnetic sensing part of the reproduction element shown in
Next, a description is given of the measurement method in the case where the magnetic head is a perpendicular recording magnetic head in the above-described method of measuring the magnetic field strength distribution of a magnetic head according to the first embodiment.
Referring to
The measurement medium 80 is formed by stacking a soft magnetic underlayer 82, a recording layer 83, the protection film 54, etc., on the substrate 51. The soft magnetic underlayer 82 is formed of a soft magnetic material, and has a magnetocrystalline easy axis in its plane. Accordingly, magnetic flux of the recording magnetic field passes in an in-plane direction.
At the time of measuring magnetic field strength distribution, laser light is emitted onto the soft magnetic underlayer 82, so that the soft magnetic underlayer 82 is heated. It is preferable that a change in the saturation magnetization of the soft magnetic underlayer 82 be smaller within the range of a change in temperature due to heating. Further, it is preferable that the change in the saturation magnetization be substantially constant (within 3% with reference to saturation magnetization at 20° C.). This makes it possible to suppress or avoid the influence of a change in the soft magnetic underlayer 82 over a change in reproduction output, so that it is possible to measure magnetic field strength with high accuracy.
Further, it is preferable that a change in the coercive force of the soft magnetic underlayer 82 be smaller within the range of a change in temperature due to heating. Further, it is preferable that the change in the coercive force be substantially constant (within 10% with reference to a coercive force at 20° C.). This makes it possible to measure the state of a magnetic field at the time of recording with more accuracy including the effect of the soft magnetic underlayer 82.
Further, the recording layer 83 is formed of, for example, CoCrPt or a CoCrPt-based alloy, and has its magnetocrystalline easy axis oriented in a direction perpendicular to the film surface. Accordingly, it is possible to measure the magnetic field strength distribution of the magnetic head 70 in the direction perpendicular to the film surface.
A recording current is supplied to the recording coil 43, so that the recording element 71 generates a recording magnetic field from the medium-opposing surface of the main magnetic pole 71b to the measurement medium 80 side. The recording magnetic field is applied to the recording layer 83 in a direction perpendicular to its film surface, and flows back to the auxiliary magnetic pole 71a through the soft magnetic underlayer 82. Accordingly, the soft magnetic underlayer 82 together with the main magnetic pole 71b substantially functions as a magnetic pole of the recording element 71. That is, the magnetic field strength distribution of the recording element 71 is formed through interaction with the measurement medium 80. Accordingly, in order to measure the recording magnetic field distribution of the perpendicular recording magnetic head 70, it is necessary to dispose the magnetic head 70 with the same configuration as at the time of actual recording and reproduction. This makes it difficult to measure the recording magnetic field strength and its distribution of a perpendicular recording magnetic head with good accuracy with the conventional method using an electron beam. On the other hand, according to this embodiment of the present invention, the magnetic field strength distribution of the magnetic head 70 is measured with the magnetic head 70 and the measurement medium 80 being disposed with the same configuration as at the time of actual recording and reproduction. Therefore, it is possible to measure the magnetic field strength distribution at the time of recording.
Referring to
The operation of the laser light emission part 16 and the action of the measurement medium 80 exposed to laser light at the time of signal recording is the same in the case of
According to this measurement method, it is possible to determine the magnetic field strength distribution of a perpendicular recording magnetic head at the time of recording, and that with good accuracy.
A method of measuring the magnetic field strength distribution of a magnetic head according to the second embodiment of the present invention is a variation of the method of measuring the magnetic field strength distribution of a magnetic head according to the first embodiment, and is the same as that of the first embodiment except for performing conversion into magnetic field strength with a different technique. Further, the same measurement apparatus, magnetic head, and principles of measurement as shown in
Referring to
Referring to
When measurement of reproduction output is completed with respect to all the levels of the recording laser power Pj (YES in step S156), in step S160, a laser power (level) Pa at which the reproduction output starts to appear is detected based on the relationship of
Preferably, the initial recording laser power P1 is set to a level at which at least the recording layer is not magnetized. This makes it possible to determine, with good accuracy, the laser power Pa at which the reproduction output starts to appear.
Further, in this step S160, a temperature Ta corresponding to the laser power Pa, at which temperature Ta the reproduction output starts to appear, is determined based on the relationship between the recording laser power Pj and the temperature of the recording layer heated by the recording laser power Pj. As a result, the temperature Ta at which the reproduction output starts to appear at the laser light exposure position Li is obtained.
Next, in steps S144 through S165, the temperature Ta is determined in the same manner with respect to the laser light exposure position Li (i=2 to n).
Next, in step S166, the temperature Ta at which the reproduction output starts to appear at each laser light exposure position Li is converted into magnetic field strength. This conversion is performed based on the relationship between the coercive force of the measurement medium and temperature shown in
This method produces the same effects as in the first embodiment. Further, according to this method, since the relationship between coercive force and temperature is employed, it is possible to perform conversion into magnetic field strength with more accuracy, so that a highly accurate magnetic field strength distribution is obtained.
In the second embodiment, it is also possible to further perform measurement of the position of the magnetic sensing part of a reproduction element shown in
According to a method of manufacturing a magnetic head according to a third embodiment of the present invention, the method of measuring the magnetic field strength distribution of a magnetic head according to the first or second embodiment is applied to a magnetic head testing process.
The magnetic head manufacturing process includes an element part forming process of forming reproduction elements and recording elements on a wafer, a flying surface forming process of forming a flying surface on each of strip-shaped row bars into which the wafer is cut, an assembling process of cutting each row bar into individual head sliders and fixing the head sliders to suspensions, and a testing process.
Referring back to
This test employs the measurement apparatus 10 of the first embodiment shown in
Still, it is possible to perform all the steps of the flowchart of
As an alternative test, it is possible to perform all the steps of the flowchart of
Further, in addition to the above-described test or alternative test, the measurement of the position of the magnetic sensing part of a reproduction element described with reference to
According to the manufacturing method of the third embodiment, it is determined whether a magnetic head is acceptable or not by indirectly or directly measuring its magnetic field strength distribution with a simple method. Accordingly, it is possible to manufacture a highly reliable magnetic head.
According to one embodiment of the present invention, there is provided a method of measuring the recording magnetic field strength distribution of a magnetic head having a recording element, the method including the steps of: (a) disposing the magnetic head at a distance from and above a measurement medium having a recording layer; (b) heating one of partial areas of the recording layer which areas oppose a medium-opposing surface of the recording element, and generating a recording magnetic field to emanate from the recording element by supplying a predetermined recording current to the recording element; (c) measuring the reproduction output of a magnetic track formed in the one of the partial areas; (d) repeating steps (b) and (c) while changing the one of the partial areas to be heated; and (e) converting the reproduction outputs obtained for the partial areas into the recording magnetic field strength distribution, wherein the one of the partial areas corresponds to a part of the medium-opposing surface of the recording element; the coercive force of the measurement medium is reduced by the heating; and step (b) heats the one of the partial areas of the recording layer to a temperature at which the coercive force of the measurement medium is lower than the strength of the magnetic field applied to the one of the partial areas from the magnetic head.
According to one embodiment of the present invention, a measurement medium is employed which, at room temperature, has a coercive force higher than the maximum recording magnetic field strength of a magnetic head to be subjected to measurement at a predetermined recording current. Then, a partial area of the recording layer of the measurement medium corresponding to a part of the medium-opposing surface of the recording element of the magnetic head is heated, so that the coercive force of the recording layer is lower in the heated area than in the other area of the recording layer. As a result, only the heated partial area is magnetized with a recording magnetic field emanating from the magnetic head, so that a magnetic track is formed therein. The reproduction output of the magnetic track is measured and converted into magnetic field strength, so that the magnetic field strength of the recording magnetic field can be detected. Further, by measuring the reproduction output corresponding to multiple laser light exposure positions while changing the position to be exposed to laser light, it is possible to determine the recording magnetic field strength distribution of the magnetic head. Accordingly, it is possible to measure magnetic field strength distribution with a simple method.
According to one embodiment of the present invention, there is provided an apparatus for measuring the recording magnetic field strength distribution of a magnetic head having a recording element, the apparatus including: a positioning part configured to position the magnetic head; a measurement medium having a substrate and a recording layer on the substrate; a heating part configured to heat the measurement medium and be capable of scanning positions to be heated; a recording part configured to form a magnetic track in the recording layer by causing the recording element to generate a recording magnetic field with one of partial areas of the recording layer corresponding to a part of the medium-opposing surface of the recording element being heated to a predetermined temperature with the heating part; a reproduction output measurement part configured to measure the reproduction output of the magnetic track; and an operation part configured to convert the reproduction output into recording magnetic field strength, wherein the coercive force of the measurement medium is reduced by the heating; and the coercive force of the measurement medium is lower than the strength of the magnetic field applied to the one of the partial areas from the magnetic head at the predetermined temperature.
According to one embodiment of the present invention, it is possible to provide a measurement apparatus capable of performing the above-described method of measuring the recording magnetic field strength distribution of a magnetic head.
According to one embodiment of the present invention, there is provided a method of manufacturing a magnetic head having a recording element, the method including a test process of testing the magnetic head, wherein the test process includes the steps of: (a) disposing the magnetic head at a distance from and above a measurement medium having a recording layer; (b) heating one of partial areas of the recording layer which areas oppose the medium-opposing surface of the recording element, and generating a recording magnetic field to emanate from the recording element by supplying a predetermined recording current to the recording element; (c) measuring the reproduction output of a magnetic track formed in the one of the partial areas; (d) repeating steps (b) and (c) while changing the one of the partial areas to be heated; (e) converting the reproduction outputs obtained for the partial areas into the recording magnetic field strength distribution; and (f) comparing positions at which the recording magnetic fields are generated or recording magnetic field strengths at the positions with a predetermined range, and determining the magnetic head as an acceptable product if the positions at which the recording magnetic fields are generated or the recording magnetic field strengths at the positions are within the predetermined range and determining the magnetic head as a defective product if the positions at which the recording magnetic fields are generated or the recording magnetic field strengths at the positions are out of the predetermined range, wherein the one of the partial areas corresponds to a part of the medium-opposing surface of the recording element; the coercive force of the measurement medium is reduced by the heating; and step (b) heats the one of the partial areas of the recording layer at a temperature at which the coercive force of the measurement medium is lower than the strength of the magnetic field applied to the one of the partial areas from the magnetic head.
According to one embodiment of the present invention, it is possible to provide a method of manufacturing a magnetic head which method can detect the recording magnetic field strength distribution of a magnetic head to be subjected to measurement with a simple method without damaging the magnetic head.
Thus, according to embodiments of the present invention, it is possible to provide a method and apparatus for measuring the recording magnetic field strength distribution of a magnetic head and a method of manufacturing a magnetic head that can measure the recording magnetic field strength distribution of the magnetic head with ease and good measurement accuracy.
The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.
For example, the reproduction head 60 is used to measure the reproduction output of a track in the measurement apparatus 10 shown in
The present application is based on Japanese Priority Patent Application No. 2006-269638, filed on Sep. 29, 2006, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-269638 | Sep 2006 | JP | national |
