Temperature‐Dependent Spin–Orbit Torques in Perpendicular Magnetic [Co/Ni]N/TbCo Composite Films

The temperature (T) dependence of spin–orbit torque (SOT) efficiencies and magnetic properties are investigated in antiferromagnetically coupled Ta/Cu/[Co/Ni]N/TbCo perpendicular composite films. By changing the Co/Ni repetition number N, the magnetization compensation temperature TM can be widely modulated, decreasing from 295 K for N = 0 to below 10 K for N = 2. From temperature‐dependent harmonic Hall measurements, it is shown that damping–like SOT field per current density χDL = HDL/Jac varies in a similar way to the net saturation magnetization MS and reaches a maximum at T = TM, whereas field‐like HFL/Jac is nearly independent with T. The observed slight deviation between χDL and 1/MS versus T curves at reduced temperatures is attributed to the increased spin Hall angle and interfacial spin transparency. It is found that the SOT efficiency ξ varies from −0.04 to −0.06 and even to −0.13 for N = 0, 1 and 2, respectively, suggesting ξ is intensively dependent on the details of the Ta/ferromagnet (FM) interface and the FM layer material. These results provide more insight into the SOT effects for exchange‐coupled perpendicular composite structures, which are valuable for developing high‐performance SOT devices. A comprehensive investigation into temperature‐dependent magnetic and transport properties is performed in a perpendicularly magnetized Ta/Cu/[Co/Ni]N = 0,1,2/TbCo system. The magnetization compensation temperature TM and spin–orbit torque efficiency ξ can be modulated by changing the Co/Ni repetition number N. It is believed that the Ta/ferromagnet (FM) interface details and FM layer material play a major role in the variation of ξ.