Disclosed is a disk for a hard disk drive. The disk includes a protective layer of shape memory alloy material over a magnetic layer. Contact between a head of the drive and the shape memory alloy material will cause frictional heat. The heat will change the crystallographic phase of the shape memory alloy material. This phase transformation process will absorb energy and reduce wear. After head-disk contact terminates the shape memory alloy material will resume its initial solid phase. The shape memory alloy material may be relatively thin thereby improving the magnetic characteristics of the disks while providing a protecting coating.
Referring to the drawings more particularly by reference numbers,
The disk drive 10 may include a plurality of heads 20 located adjacent to the disks 12. The heads 20 may have separate write and read elements (not shown) that magnetize and sense the magnetic fields of the disks 12.
Each head 20 may be gimbal mounted to a flexure arm 22 as part of a head gimbal assembly (HGA). The flexure arms 22 are attached to an actuator arm 24 that is pivotally mounted to the base plate 16 by a bearing assembly 26. A voice coil 28 is attached to the actuator arm 24. The voice coil 28 is coupled to a magnet assembly 30 to create a voice coil motor (VCM) 32. Providing a current to the voice coil 28 will create a torque that swings the actuator arm 24 and moves the heads 20 across the disks 12.
Each head 20 has an air bearing surface (not shown) that cooperates with an air flow created by the rotating disks 12 to generate an air bearing. The air bearing separates the head 20 from the disk surface to minimize contact and wear.
The hard disk drive 10 may include a printed circuit board assembly 34 that includes a plurality of integrated circuits 36 coupled to a printed circuit board 38. The printed circuit board 38 is coupled to the voice coil 28, heads 20 and spindle motor 14 by wires (not shown).
Alternatively, a layer of SMA material may be located between the substrate 50 and the magnetic layer 52, in addition to, or alternatively to the SMA layer 54. The SMA 54 can be covered with a layer of DLC material 56 and a layer of lubricant 58. The SMA material between the substrate 50 and magnetic layer 52 may have a thickness between 3 angstroms to 1 mm.
When a head 20 makes contact with a rotating disks the contact will cause thermal energy. The thermal energy causes the shape memory alloy material 54 to change phase to a more compliant material. The phase transformation absorbs the mechanical energy of the head-disk contact. After the head-disk contact event is terminated the shape memory alloy 54 reverts back to the original solid phase.
The layer of shape memory alloy material 54 may be relatively thin to improve the magnetic characteristics of the disks. By way of example, the layer of shape memory alloy material 54 may have a thickness between 3 and 10 mm. The shape memory alloy material 54 may be covered with a layer of lubricant 56 to reduce the friction between head 20 and the disk 12.
By way of example, the anti-ferromagnetic material may be constructed from a platinum and manganese composition PtMn, or an iridium and manganese composition IrMn. By way of example, the IrMn may be by atomic 20% iridium and 80% manganese. The synthetic AFC type soft magnetic layers 74 and 76 are pinned by the anti-ferromagnetic layer to increase the SNR. The SNR is improved by lowering the DC noise and spike noise within the soft magnetic layers 74 and 76 of the media.
It has been found that the media provides a higher SNR if the bottom soft magnetic underlayer 74 has a high magnetic saturation characteristic and the top soft magnetic underlayer 76 has a low magnetic saturation characteristic. By way of example, the bottom soft magnetic underlayer 74 may be constructed with cobalt, zirconium and niobium CoZrNb. The top soft magnetic underlayer 76 may be constructed from nickel, iron and niobium NiFeNb. The intermediate layer may be constructed from ruthenium.
The media may further include layers of ruthenium 80 and tantalum 82 adjacent to the top soft magnetic under layer 76. The media may also include magnetic recording layer 84.
A layer of shape memory alloy 86 covers the magnetic recording layer 84. To reduce friction between the head and the disk, the outer disk surface may include a layer of lubricant 88.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.