Magnetic materials for hard-disk heads use the same magnetic tunnel junctions (MTJs) as do the MRAMs IBM announced it was developing with TDK last week. Now, the U.S. National Institute of Standards and Technology (NIST) claims to have invented a process for fine-tuning MTJs for the next generation of HD heads, and perhaps even to enable denser MRAMs. "Our process was developed to show hard-disk head manufacturers how to fine tune the resistance of the buffer layer in their heads, but it may also help to improve the MTJs for denser MRAMs," said NIST physicist Josh Pomeroy.
With every semiconductor generation, engineers shrink devices more and more, which, unfortunately, changes the resistance of insulators—so-called buffer layers—especially when these films go below one nanometer thick, at which point they comprise of only a few atomic layers.
Particularly affected by this phenomenon, according to NIST, are hard-disk recording heads, which are currently caught between having too much resistance and too little—with an unreachable gap in-between. However, NIST claims to have a solution that enables engineers to regain fine-control over the resistance of films no matter how thin, and retarget their resistance anywhere in the gap, thereby improving MTJs for hard-disk heads and MRAMs.
The new process directs a controlled beam of xenon +44 ions, each with 50,000 electron volts of potential energy, onto the insulating film, thereby precisely perforating it and lowering its resistance. The process—which typically creates from 1000 to 100,000 tiny holes in the aluminum oxide insulating film in a single hard-disk recording head—yields access to nearly any resistance value between zero and infinity. This gives engineers control over the resistance of films even if they are only a few atomic layers thick.