  Rotating the magnetization of a magnetostrictive nanomagnet with electrically
generated mechanical strain dissipates miniscule amount of energy compared to
any other rotation method and would have been the ideal method to write bits in
nonvolatile magnetic memory, except strain cannot ordinarily rotate the
magnetization of magnet by more than 90 degrees and "flip" it. Here, we
describe a scheme to achieve complete 180 degree rotation of the magnetization
of a nanomagnet with strain that will enable writing of binary bits in
non-volatile magnetic memory implemented with magneto-tunneling junctions whose
soft layers are two-phase magnetostrictive/piezoelectric multiferroics. At room
temperature, this writing method results in: (1) energy dissipation < 6200 kT
per bit, (2) write error probability < 10^-6, (3) write time of ~ 1 ns, and (4)
low read error. This could potentially lead to a new genre of non-volatile
memory that is extremely reliable, fast and, at the same time,
ultra-energy-efficient.
