Intrinsic magnetoresistance in metal films on ferromagnetic insulators

We predict a magnetoresistance induced by the interfacial Rashba spin-orbit coupling in normal metal/ferromagnetic insulator bilayers. It depends on the angle between current and magnetization directions as found for the “spin Hall magnetoresistance” mechanism, i.e., the combined action of spin Hall and inverse spin Hall effects. By the identical phenomenology it is not obvious whether the magnetoresistance reported by Nakayama et al. [Phys. Rev. Lett. 110, 206601 (2013)] is a bulk metal or interface effect. The interfacial Rashba-induced magnetoresistance may be distinguished from the bulk metal spin Hall magnetoresistance by its dependence on the metal film thickness.

Figure 1

Schematic picture of the system.

Figure 2

Top: A schematic picture of the rotating magnetizations of FI. Bottom: The longitudinal (solid red) and transverse (dashed blue) conductivity: ${\rho }_{xx}^m$ normalized by ${\rho }_{xx}^m(\alpha =\pi /2)$ and ${\rho }_{xy}^m$ by ${\rho }_{xy}^m(\alpha =-\pi /4)$ in the NM/FI system as a function of the magnetization angle.

Figure 3

The NM film thickness $d$ dependence of the longitudinal conductivity ${\sigma }_{xx}$ for $\mathbf{M}\parallel \widehat{\mathbf{y}}$ ($\alpha =-\pi /2$, solid curve), the longitudinal/transverse magnetoconductivity ${\sigma }_{xx}^m={\sigma }_{xy}^m=\left|{\sigma }_{xy}\right|$ (dashed curve), and the limiting longitudinal conductivity for large $d$ (dotted curve). The longitudinal conductivity has a minimum at $d/d_{\eta }=\sqrt{9/20}$.