The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields 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 volume of information processing in the information age is increasing rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
However, the further miniaturization of the various components, particularly, the size and/or pitch of magnetic grains, presents its own set of challenges and obstacles in conventional HDD products. Noise performance and spatial resolution are key parameters in magnetic recording media and are ongoing challenges to advance the achievable areal density of media. The dominant media noise source today is transition jitter. In sputtered media, it reflects the finite size, random positioning and dispersions in size, orientation and magnetic properties of the fine grains that comprise the media.
In order to address grain size and transition jitter it was proposed to change the recording mechanism from conventional magnetic field recording to HAMR, also known as “thermally assisted magnetic recording” TAR or TAMR. HAMR recording employs heat to lower the effective coercivity of a localized region on the magnetic media surface and write data within this heated region. The data state becomes stored, or “fixed,” upon cooling the media to ambient temperatures. HAMR techniques can be applied to longitudinal and/or perpendicular recording systems, although the highest density state of the art storage systems are more likely to be perpendicular recording systems. Heating of the media surface has been accomplished by a number of techniques such as focused laser beams or near field optical sources.
However, these techniques for heating the media surface during HAMR recording also cause the temperature of the HAMR heads themselves to increase, thereby inducing thermal expansion. As a result, the HAMR heads expand towards the media. Yet, as the distance between the media and a media facing side of the HAMR head fluctuates with heating and cooling thereof, so does the field strength applied to the medium when writing during expansion, and consequently the signal strength observed during readback. Conventional products are thereby afflicted by inconsistent read and write reliability.
In sharp contrast, various embodiments herein implement a heating device that is preferably able to achieve an about constant spacing between a media facing side of a head and a medium during reading and/or writing thereto, as will be described in further detail below.