MnBi Thin Films: Physical Properties and Memory Applications

Abstract
Thin films of MnBi possess many unusual physical properties and are particularly suitable for memory applications using laser Curie‐point writing and magneto‐optical readout. Films prepared on mica substrates have the easy direction of magnetization perpendicular to the film plane. They typically have a specific Faraday rotation of 5×105 deg/cm, and an absorption coefficient of 3.8×105 cm−1 for 6328 Å wavelength, permitting a readout rate of 109 bits/sec at 1 mW laser power level using available detectors. Curie‐point writing and erasing of a spot a few microns in diameter in a 1000 Å thick film with a 4 μsec pulse from a 13 mW Gaussian laser beam have been achieved. For a 106 bits/cm2 packing density, heating at adjacent spots is negligible. Calculations show that the writing magnetic field can be reduced to less than 10 Oe by using a memory plane consisting of discrete squares of MnBi. Analytical and experimental results as well as memory design considerations are presented.

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