www.nanopicoftheday.org
June 7, 2004
Source: Stephen Russek
References:
Description:
NIST researchers studying the dynamics of magnetization reversal in spin-valve devices with submicrometer dimensions have overcome a primary technical hurdle for precise control of the switching of these devices. Spin-valve devices are being actively developed by several companies for use as recording bits in non-volatile magnetic random access memory (MRAM). In a spin-valve, only one ferromagnetic layer, the “free layer,” responds to external fields. Internal magnetic fields within the device allow only two stable magnetization directions, 180 degrees apart, along an easy axis. Current implementation of MRAM requires field pulses to be applied for 10 to 20 nanoseconds along either the positive or negative easy axis, depending on the desired state. The NIST researchers discovered a way to switch the devices using field pulses of less than 300 picoseconds duration directed perpendicular to the easy axis. The magnetization is reversed due to large-angle precessional motion. Precessional switching requires only a single polarity pulse applied perpendicular to the device easy axis, which results in a toggle operation of the magnetic state of the device.
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