[20p-B101-1~12] 10.3 Spin devices, magnetic memories and storages

▼ [20p-B101-4] Stochastic magnetic tunnel junctions with double free layers

〇Rikuto Ota^1,2, Keito Kobayashi^1,2, Keisuke Hayakawa¹, Shun Kanai^1,3,4,5, Kerem Camsari⁶, Hideo Ohno^1,5,7,8, Shunsuke Fukami^1,2,5,7,8,9 (1.LNS, RIEC, Tohoku Univ., 2.Grad. School Eng., Tohoku Univ., 3.PRESTO, JST, 4.DEFS, Tohoku Univ., 5.CSIS, Tohoku Univ., 6.Dept. Elec. and Comp. Eng., UCSB., 7.WPI-AIMR, Tohoku Univ., 8.CIES, Tohoku Univ., 9.Inamori Research Institute for Science)

Keywords:spintronics, probabilistic computers, stochastic magnetic tunnel junctions

Stochastic magnetic tunnel junctions (s-MTJs) are gathering attention as a key element for probabilistic computers. For the application, the s-MTJs are preferred to have a simple and scalable structure and to be insensitive to bias voltage. Previous theoretical work proposed s-MTJs with a double-free-layer structure, which meet these demands. In this work, we prepare the double-free-layer s-MTJs and measure their properties.
We measure the rf transmitted voltage of the s-MTJs under various bias voltages. We observe a random telegraph noise reflecting the two magnetization configurations, the fundamental operation for probabilistic computers. We measure the magnetic field (shift field) at which the MTJ takes parallel and antiparallel states with an equal probability and the relaxation time. Under the bias voltages between -600 mV and 600 mV, small variations of the shift field and relaxation time, which the theory predicted are confirmed; less than 5% for the former and a factor of 2 for the latter, indicating that the both layers fluctuate with time as expected.