Yuichi Osawa

Low-Current High-Speed Spin-Transfer Switching in a Perpendicular Magnetic Tunnel Junction for Cache Memory in Mobile Processors

The efficiency of the power reduction in a normally off mobile processor employing spin-transfer torque magnetoresistive random access memory-based cache memory strongly depends on the write charge, which is the value of the write pulsewidth multiplied by the write current. We studied the spin-transfer switching probability (Psw) in a perpendicular magnetic tunnel junction (p-MTJ) with the aim of achieving high-speed switching of less than a few nanoseconds at a low current below 100 μA. High-speed switching faster than 1 ns was observed at a write current below 100 μA. To understand the observed pulsewidth dependence of Psw, analysis using a macrospin model based on a dynamic switching was carried out. The analysis reproduced the nature of the Psw distributions quantitatively. In addition, the developed analysis suggested the effectiveness of miniaturizing the storage layer to reduce the switching current. The p-MTJ operated continuously without any error at a write pulsewidth of 2 ns and current of 49 μA.