Curie point written magnetoresistive memory

Abstract

Memory cells have been fabricated and tested to demonstrate storage in the pinned layer of a giant magnetoresistance (GMR) spin valve film. The spin valve was top pinned with a FeMn film and gave about 4% GMR ratio. The memory cell consisted of an oblong, 0.6 μm×7.0 μm GMR bit with first metal contacts at each end and a perpendicular first and second metal word line passing over the bit. Joule heating due to current pulses through both the memory cell and the word line raised the temperature of the FeMn pinning layer above its Néel point. The magnetic field generated by the word line current switched the pinning direction, depending on the polarity of the word line current. Sense line currents up to 5 mA provided a half select without disturbing the bit. In combination with a 5 mA sense current, the bit was written with a word current pulse of 190 mA. The improved thermal stability of the pinned storage layer memory cell is shown to become necessary as the size of a magnetoresistive memory cell drops below about 0.1 μm×0.4 μm.