Patent Application
20080212235
The present invention relates to magnetic data recording, and more particularly to a slider having an air bearing surface design for damping slider oscillations during flight over a magnetic disk.
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.
The write head has traditionally included a coil layer embedded in first, second and third insulation layers (insulation stack), the insulation stack being sandwiched between first and second pole piece layers. A gap is formed between the first and second pole piece layers by a gap layer at an air bearing surface (ABS) of the write head and the pole piece layers are connected at a back gap. Current conducted to the coil layer induces a magnetic flux in the pole pieces which causes a magnetic field to fringe out at a write gap at the ABS for the purpose of writing the aforementioned magnetic transitions in tracks on the moving media, such as in circular tracks on the aforementioned rotating disk.
In recent read head designs a spin valve sensor, also referred to as a giant magnetoresistive (GMR) sensor, has been employed for sensing magnetic fields from the rotating magnetic disk. The sensor include a nonmagnetic conductive layer, referred to as a spacer 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 spin valve sensor for conducting a sense current therethrough. The magnetization of the pinned layer is pinned perpendicular to the air bearing surface (ABS) and the magnetic moment of the free layer is located parallel to 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.
The thickness of the spacer layer is chosen to be less than the mean free path of conduction electrons through the sensor. When this arrangement, a portion of the conduction electrons is scattered by the interfaces of the spacer layer with each of the pinned and free layers. When the magnetizations of the pinned and free layers are parallel with respect to one another, scattering is minimal and when the magnetization of the pinned and free layer are antiparallel, scattering is maximized. Changes in scattering alter the resistance of the spin valve sensor in proportion to cosθ, where θ is the angle between the magnetizations of the pinned and free layers. In a read mode the resistance of the spin valve sensor changes proportionally to the magnitudes of the magnetic fields from the rotating disk. When a sense current is conducted through the spin valve sensor, resistance changes cause potential changes that are detected and processed as playback signals.
In order to maximize the magnetic performance of a data recording system, it is necessary to minimize the fly height of a slider over a disk. Minimizing the fly height of the slider allows the read sensor and write head to be as close as possible to the magnetic medium. Current and future magnetic recording systems, therefore, have fly heights that are extremely small. One problem presented by such extremely small fly heights is that oscillations or vibrations can occur when the slider is disturbed, such that the slider begins to modulate or “bounce” over the disk. Large oscillatory motion of the slider, therefore, may result in contact between the magnetic read/write head and the disk surface. This catastrophic contact can result in significant data loss, and even permanent damage to the disk and to the read/write head.
Therefore, there is a strong felt need for a data recording system design that can allow very small fly heights while also preventing oscillatory motion of the slider over the disk. Such a design would preferably achieve these goals with minimal additional manufacturing or design complexity or cost.
The present invention provide a slider for magnetic data recording. The slider has an air bearing surface with a trailing edge pad that is configured with a series of recesses that damp slider oscillation during use. The series of recesses formed in the trailing pad of the slider reduce slider oscillations by creating localized pressure gradients within the generally high pressure area over the pad.
The slider can be configured with a raised primary pad and a secondary raised pad formed on the primary raised pad. A series of recesses formed in the secondary pad prevent slider oscillations, which would otherwise be especially problematic in a slider having such a secondary raised pad and associated higher pressure area thereover.
The recesses formed in the ABS can be of many different configurations. For example, the recesses can be discrete shapes such as squares, circles, triangles or irregular shapes. The recesses can also be configured as a series of trenches, which can be straight or curved and could be irregular, serpentine, or could be arranged in a random or interlocking manner such as a labyrinth structure.
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, slider 113 moves radially in and out over the disk surface 122 so that the magnetic head assembly 121 may access different tracts 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. The above description of a typical magnetic disk storage system, and the accompanying illustration of
With reference to
With reference now to
When current flows through the coil 328, a magnetic flux flows through the magnetic yoke 331. This causes a magnetic field to fringe out at the ABS across the write gap formed by the non-magnetic gap material 316. This fringing magnetic field can then write a magnetic signal onto an adjacent magnetic medium (not shown). This signal can be ready back by the magnetoresistive sensor 310, which can be a giant magnetoresistive sensor (GMR), tunnel junction sensor (TMR) or any other type of magnetoresistive sensor.
Although a particular embodiment of a magnetic head 302 has been shown and described above, this is only for purposes of illustrating an environment in which the present invention can be implemented. Virtually any type of read and write head can be employed in the present invention. For example, the write head could be designed for perpendicular magnetic recording and could include more than one write coil or could include a helical coil or a pancake coil.
With reference now to
As discussed above, magnetic recording systems have suffered from fly height oscillations when the slider is disturbed from its steady-state fly-height. At very low fly heights, the slider can begin to oscillate between high and low fly heights, causing the slider to actually bounce on the medium in the extreme case. This, of course leads to damaging head disk contact (crashing) which can result in data loss or, even worse, can lead to permanently damaging the read/write heads.
As can be seen, the pad 206 is configured with a pattern of recessed shapes 402. These recesses 402 are shown as squares in
With reference to
With reference to
Unfortunately, the pressure under the secondary pad becomes so great during burnishing or actual use that the problem of fly height oscillations is exacerbated by the use of such as secondary pad 606. Therefore, the localized pressure gradients and pressure relief provided by the present invention provides even greater advantage with use in slider 113 having such a secondary pad design.
In addition, slider bouncing during burnishing is particularly problematic. Since the slider is designed to be in contact with the disk at least at some point during burnishing, the bouncing of the slider 602 can cause even greater damage to the disk or read/write head. In addition, the uneven burnishing caused by the slider bouncing can cause unwanted ABS surface irregularities and can result in unwanted flying height changes.
To this end, as shown in
While various embodiments have been described, 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.
