Energy Efficient Spintronic Devices for Memory and Computing by New Materials, New Physics and Voltage Control

Spin-orbit torque (SOT) is a promising mechanism for next-generation memory and logic devices that could surpass traditional CMOS technology. However, the low SOT efficiency and the need for an external magnetic field in existing materials have limited industrial adoption. To overcome these challenges, we proposed and experimentally demonstrated new SOT materials and voltage-controlled device architectures. In this talk, I will first focus on Ni₄W, a newly identified unconventional SOT material with high efficiency and intrinsic field-free switching capability. These properties arises from Ni₄W’s low crystalline symmetry, which enables spin polarization along multiple directions and breaks the system’s symmetry. Epitaxial Ni₄W thin films with high crystalline quality were grown using magnetron sputtering. Harmonic Hall measurements revealed a Y-spin SOT efficiency of 0.73 and a Z-spin efficiency of 0.02 at room temperature—among the highest for unconventional SOT materials reported [1]. We further demonstrated deterministic field-free switching of perpendicular magnets with 40% lower current density than Pt.

In the second part of the talk, I will introduce our work on voltage-controlled spintronic devices, utilizing a newly proposed electron-depletion-based voltage-controlled magnetic anisotropy (ED-VCMA) and a recently demonstrated new switching mechanism: voltage-controlled exchange coupling (VCEC). VCMA is a well-known solution for achieving low switching current by reducing the energy barrier of the ferromagnetic material through the application of an additional electric field. By applying electron depletion physics with a work-function-engineered underlayer, the VCMA coefficient can be further enhanced [2]. VCEC is a mechanism by which an applied voltage modulates both the direction and strength of interlayer magnetic exchange interactions. By integrating VCEC into a superparamagnetic magnetic tunnel junction (MTJ), we demonstrate device-level bipolar switching with an associated power consumption of only 40 nW, about two orders of magnitude lower than that of spin-transfer torque (STT) switching [3].

[1]         Y. Yang et al., Advanced Materials, p. 2416763 (2025).

[2]         Y.-C Chan et al, ACS nano 19.16, 15953-15962. (2025).

[3]         Q. Jia et al., Nano Letter, 25 (23), 9181–9188 (2025).