A magnetoresistive random access memory (MRAM) is
a universal nonvolatile memory with fast read/write speed
and unlimited endurance. So far, however, it has been
impossible to design a Gbit-density MRAM.
The most important issue in this regard is to
significantly decrease the writing current. Toshiba has
been developing a spin-transfer-torque writing technology
with perpendicular magnetoresistive tunnel junctions
(MTJs). We have successfully demonstrated a small
writing current lower than 50 ľA using our original
perpendicular MTJs. This is the smallest current ever
reported for nonvolatile MTJs. Further, fast writing with a
writing current pulse of 4 ns has also been demonstrated.
These results have opened the way for the use of
MRAMs in the main memory of PCs.
This work was partially supported by the New Energy and
Industrial Technology Development Organization (NEDO).
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