Spin-orbit torque switching in Co/Ni multilayers with strong domain wall pinning

Abstract

Spin–orbit torque (SOT) switching is a promising candidate mechanism to be applied in the spintronic devices. Here, we report the SOT switching in the [Co/Ni] × n multilayers with maze domain structures. The experimental results show that the SOT switching efficiency strongly depends on the magnetic structure of the ferromagnet (FM) layer. With the increase in cycle number of [Co/Ni] × n multilayers, the switching ratio rapidly decreases, even cannot present the magnetization switching. This switching behavior can be attributed to the strong domain wall pinning in the samples with the maze domain structure. Moreover, although the samples in this work have the same spin current sources, the estimated SOT efficiencies vary greatly, suggesting that the SOT efficiency in a FM/heavy metal (HM) structure depends not only on the spin Hall effect and/or Rashba effect but also on the magnetic structure of FM layer. This work provides a better understanding for the nature of SOT switching in the FM/HM heterostructures with maze domain.