Patent Application
20120250178
The present invention relates to magnetic heads for data recording, and more particularly to a magnetic media having a thermal insulation layer for reduced energy consumption in thermally assisted data recording.
The heart of a computer's long term memory is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
A giant magnetoresistive (GMR) or tunnel junction magnetoresistive (TMR) sensor senses magnetic fields from the rotating magnetic disk. The sensor includes a nonmagnetic conductive layer, or barrier layer, sandwiched between first and second ferromagnetic layers, referred to as a pinned layer and a free layer. First and second leads are connected to the sensor for conducting a sense current there-through. The magnetization of the pinned layer is pinned perpendicular to the air bearing surface (ABS) and the magnetic moment of the free layer is biased parallel with the ABS, but free to rotate in response to external magnetic fields. The magnetization of the pinned layer is typically pinned by exchange coupling with an antiferromagnetic layer.
In a perpendicular magnetic recording system, the magnetic media has a magnetically soft underlayer covered by a thin magnetically hard top layer. The perpendicular write head has a write pole with a very small cross section and a return pole having a much larger cross section. A strong, highly concentrated magnetic field emits from the write pole in a direction perpendicular to the magnetic disk surface, magnetizing the magnetically hard top layer. The resulting magnetic flux then travels through the soft underlayer, returning to the return pole where it is sufficiently spread out and weak that it will not erase the signal recorded by the write pole when it passes back through the magnetically hard top layer on its way back to the return pole.
In order to optimize performance, the magnetic media must easily switch magnetization directions in response to a magnetic field from the write head. However, in order to be magnetically stable, these magnetizations must remain, even when the magnetic media is subjected to high temperature. This means that the magnetic media must have a high magnetic coercivity in order to prevent data loss. Such a media can, however, be difficult to write onto.
Thermally assisted recording can be used to overcome this problem, allowing data to be written onto a magnetically stable, high coercivity media. The media is heated, such as by a laser in order to temporarily lower the coercivity of the media while the data is being written. The media then cools, raising the coercivity to allow the media to be stable. In order to minimize the power consumption of the device, it is necessary that the heating be as efficient as possible. It is therefore, desirable to maximize heating efficiency to allow as little power consumption from the heating device (e.g. laser) as possible.
The present invention provides a magnetic media for magnetic data recording that includes a substrate and a thermal insulation structure formed over the substrate. A low coercivity magnetic layer is formed over the thermal insulation layer, and a non-magnetic layer is sandwiched between the low coercivity layer and a magnetic write layer.
The present invention increases the efficiency of thermally assisted writing by greatly reducing the amount of heat that is lost to the substrate. This reduction in heat lost to the media substrate allows for reduced power consumption of the heating element.
Further insulation benefits can be achieved by increasing the number of oxide layers and NiTa layers in the thermal insulation structure. For example, the insulation structure can include three or four oxide layers with alternating NiTa layers.
These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the Figures in which like reference numerals indicate like elements throughout.
For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings which are not to scale.
The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein.
Referring now to
At least one slider 113 is positioned near the magnetic disk 112, each slider 113 supporting one or more magnetic head assemblies 121. As the magnetic disk rotates, the slider 113 moves radially in and out over the disk surface 122 so that the magnetic head assembly 121 may access different tracks of the magnetic disk where desired data are written. Each slider 113 is attached to an actuator arm 119 by way of a suspension 115. The suspension 115 provides a slight spring force which biases slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator means 127. The actuator means 127 as shown in
During operation of the disk storage system, the rotation of the magnetic disk 112 generates an air bearing between the slider 113 and the disk surface 122 which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension 115 and supports slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation.
The various components of the disk storage system are controlled in operation by control signals generated by control unit 129, such as access control signals and internal clock signals. Typically, the control unit 129 comprises logic control circuits, storage means and a microprocessor. The control unit 129 generates control signals to control various system operations such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide the desired current profiles to optimally move and position slider 113 to the desired data track on disk 112. Write and read signals are communicated to and from write and read heads 121 by way of recording channel 125.
As described above, thermally assisted magnetic recording can be used to increase the writeability of a high coercivity magnetic media. A heating device such as a laser (not shown in
With reference now to
A high permeability magnetic layer 308 is then formed on the thermal insulation layer 318. This magnetically soft layer 308 can be a material such as FeCoTaZr. A non-magnetic decoupling structure 309 can be formed over the magnetically soft layer 308. The decoupling layer 309 can be constructed as a pair of layers of Ru 310, 312. The lower Ru layer 310 is deposited at a relatively low pressure, whereas the upper Ru layer 312 is deposited at a relatively higher pressure. A high coercivity magnetic write layer 314 is formed over the decoupling structure 309. The magnetic write layer 314 is a high coercivity magnetic material such as (CoPtCr—SiO2 or Ll0 FeNiPtAg—X where X is a segregant material such as an oxide, nitride, or carbide), that can maintain a stable magnetization after being magnetized by a writer 324.
The slider 113 described above with regard to
As described above, in order for the magnetic media to be magnetically stable and maintain its magnetization over long periods of time and at high temperatures, the layer 314 must have a very high magnetic coercivity. While this high coercivity ensures that the magnetic signal written to the layer 314 will be magnetically stable, it also means that it is very hard to magnetize the layer 314. In order to make it easier to write to the magnetic layer 314, a heating element 328 is provided to locally heat the magnetic layer 314 just prior to writing. This heating element 328 is preferably a waveguide that can guide light from a laser to a desired point on the slider 121 for heating a portion of the disk 302. Alternatively, another heating device, such as a resistive heater, could be used to locally heat the disk.
In order to effectively assist in writing to the layer 314, the heating element 328 must heat the layer 314 to a high enough temperature to lower the magnetic coercivity of the layer 314. What's more, the layer 314 must remain at this high temperature until the write pole 330 has reached this location. As discussed above, in prior art systems the substrate 304 has provided a large heat sink which has quickly dissipated heat away from the layer 314. This has required a larger amount of heat to be generated from the heat source 328 in order to compensate for this heat sink effect. The excessive cooling caused by this heat sink effect causes the temperature of the layer 314 to drop quickly, requiring a larger heating from the heating element to ensure that the layer 314 is still hot enough when the write pole 330 reaches this location.
In the present invention however, the presence of the thermal insulation structure 318 prevents this heat sink effect by providing a thermal barrier between the layers 314, 308 and the substrate 304. This advantageously allows the magnetic write layer 314 to be heated to the necessary temperature with much less power consumption from the heating element 328. In addition, this also advantageously allows the layer 314 to remain at this elevated temperature for a longer duration, ensuring that this temperature is maintained when the write pole 330 passes over the heated location. The relative locations of the elements of the magnetic head 121 are for purposes of illustration, and can be arranged in other ways. For example, the heating element 328 could be located adjacent to the write pole 330, such as between the write pole 330 and return pole 332. In addition the write head 324 can include other elements not shown such as, but not limited to, a wrap-around trailing magnetic shield. These elements have not been shown in
With reference now to
The benefits derived from the above described structures can be better understood with reference to
Therefore, it can be seen, that the novel media structure disclosed provides a very significant benefit in overall system performance, reducing the amount of power needed to heat a media to a sufficiently high temperature to assist in writing to the media. In addition, the provision of multiple layers and multiple interfaces in the structure further increase the thermal insulation. While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
