Unambiguous experimental demonstration of magnon transfer torque effect

Spin torque provides convenient electric means to efficiently control magnetizations. It can usually be produced by spin-polarized current or pure spin current via spin Hall effect. The former and the latter are named as spin transfer torque (STT) and spin orbit torque (SOT), respectively. Utilizing these tools, people have developed the second generation STT-MRAM (Magnetic Random-Access Memory) with in-plane magnetic anisotropy, the third generation STT-MRAM with perpendicular magnetic anisotropy and the fourth generation SOT-MRAM among other spintronic devices and chips. Moreover, perpendicular STT-MRAM chips have been demonstrated and close to large-scale applications.