Negative spin Hall magnetoresistance of Pt on the bulk easy-plane antiferromagnet NiO

Abstract

We report on spin Hall magnetoresistance (SMR) measurements of Pt Hall bars on the antiferromagnetic NiO(111) single crystal. An SMR with a sign opposite of conventional SMR is observed over a wide range of temperatures as well as magnetic fields stronger than 0.25T. The negative sign of the SMR can be explained by the alignment of magnetic moments being almost perpendicular to the external magnetic field within the easy plane (111) of the antiferromagnet. This correlation of magnetic moment alignment and external magnetic field direction is realized just by the easy-plane nature of the material without the need of any exchange coupling to an additional ferromagnet. The SMR signal strength decreases with increasing temperature, primarily due to the decrease in Néel order by including fluctuations. An increasing magnetic field increases the SMR signal strength as there are less domains and the magnetic moments are more strongly manipulated at high magnetic fields. The SMR is saturated at an applied magnetic field of $6$~T resulting in a spin-mixing conductance of $\sim 10^{18}{\Omega }^{-1}$m${}^{-2}$, which is comparable to that of Pt on insulating ferrimagnets such as yttrium iron garnet. An argon plasma treatment doubles the spin-mixing conductance.

References in corpus (7)

• Theory of spin Hall magnetoresistance
• Spin pumping and spin-transfer torques in antiferromagnets
• Superfluid spin transport through antiferromagnetic insulators
• Simultaneous detection of the spin-Hall magnetoresistance and the spin-Seebeck effect in Platinum and Tantalum on Yttrium Iron Garnet
• Surface sensitivity of the spin Seebeck effect
• Electrical detection of spiral spin structures in Pt|Cu_2OSeO_3 heterostructures
• Impact of the interface quality of Pt/YIG(111) hybrids on their spin Hall magnetoresistance

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