These challenges required the development of nano-scale surface plasmons (surface guided laser) instead of direct laser-based heating, new types of glass platters and heat-control coatings that tolerate rapid spot-heating without affecting the contact with the recording head or nearby data, new methods to mount the heating laser onto the drive head, and a wide range of other technical, development and control issues that needed to be overcome.
[3] In effect, a point exists at which it becomes impractical or impossible to make a working disk drive because magnetic writing activity is no longer possible on such a small scale.
[2] Traditional plated magnetic platters are also not suitable due to their heat conduction properties, so new drive materials must be developed.
[2] Seagate, which has been prominent in the development of HAMR drives, commented that the challenges include "attaching and aligning a semiconductor diode laser to an HDD write head and implementing near-field optics to deliver the heat", along with the scale of use which is far greater than previous near-field optic uses.
[2] Based on the idea of a waveguide, the laser "travels" along the surface of a guiding material, which is shaped and positioned in order to lead the beam to the area to be heated (about to be written).
Diffraction does not adversely affect this kind of wave-guide based focus, so the heating effect can be targeted to the necessary tiny region.
[2] Running costs are not expected to differ significantly from non-HAMR drives, since the laser only uses a small amount of power – initially described in 2013 as a few tens of milliwatts[1] and more recently in 2017 as "under 200mW" (0.2 W).
Single-head transfer reliability was reported to be "over 2 PB" (equivalent to "over 35 PB in a 5 year life on a 12 TB drive", stated to be "far in excess" of typical use), and heating laser power required "under 200mW" (0.2 W), less than 2.5% of the 8 or more watts typically used by a hard drive motor and its head assembly.
A permanent magnetic strip is deposited on a substrate of silicon or glass, and this is irradiated by a laser beam through a pre-designed mask.
The mask is designed specifically for this purpose to prevent the laser beam from irradiating some portions on the magnetic film.