One trick used in high density hard files is two layers of magnetic media with a thin neutral layer between them, each later is magnetized oppositely which is supposed to element room temperature self erasure.
The high density high speed hard files I installed in the digital video edit suites were made this way.
I have no idea how well it works, the people I installled the systems for sold their business to a national chain with their own tech support.
?
It seems as though the neutral layer was 3 or 4 atoms thick.
?
All media fails in the long run.
?
