Manipulation of spin Hall magnetoresistance and unidirectional spin Hall magnetoresistance in Ta/Pt/CoFeB multilayers

• Published in: Journal of magnetism and magnetic materials Vol. 560; p. 169667
• Main Authors: Li, Wangda, Zheng, Yuqiang, Luo, Keliu, Han, Bo, Zhang, Bo, Guo, Yonghai, Cao, Jiangwei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2022
• Subjects: Spin accumulation; Spin diffusion equation; Spin Hall effect; Spin Hall magnetoresistance; Unidirectional Spin Hall magnetoresistance; Spin accumulation; Spin Hall magnetoresistance; Unidirectional Spin Hall magnetoresistance; Spin diffusion equation; Spin Hall effect
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2022.169667

•The competition between the spin current from Ta and Pt is observed in the Pt thickness dependence of SMR and USMR.•The SMR and unidirectional SMR theory based on spin diffusion equation is extended to a tri-layer structure.•The Pt thickness dependence of SMR and USMR were well fitted by using the same spin transport parameters of Pt. The interaction between spin current and magnetic moments in heavy metal (HM)/ferromagnetic (FM) structure results in the well-known spin orbit torque and the concomitant magnetoresistance effect: spin Hall magnetoresistance (SMR) and the unidirectional SMR (USMR). In this work, we simultaneously investigated the SMR and USMR in Ta/Pt/CoFeB/MgO multilayers with different Pt thickness (tPt) by the harmonic measurements. It is observed that at tPt≈0.9nm, the SMR is close to zero and the polarity of USMR reverses, which originate from the competition of the spin current from Ta and Pt layers. Under the theoretical framework of the spin diffusion equation, we derived the theoretical expressions of SMR and USMR in the tri-layer magnetic heterostructures. We found that the tPt dependences of the SMR and USMR can be well fitted by the expressions, from which the spin transport parameters of Pt were extracted. Our work provides a fundamental insight into spin transport in the system with two heavy-metal layers, and a possible way to control SMR and USMR of HM/FM systems.