Modeling spin transport through insulator interfaces

Experiments have shown spin transport enhancement by a thin antiferromagnetic insulator between a metal and a ferromagnetic insulator [1]. While previous theoretical work [2] was able to reproduce some of the features of those experiments, the role of the interface is taken into account typically by a single parameter that is fit to experimental data.

We consider a model of a thin layer NiO oriented in (111) direction, sandwiched between a metal and a ferromagnetic insulator. We take into account nearest and next-nearest neighbor exchange coupling at the interfaces as well as different magnetic order. We compute the spin current through this system driven either by a thermal gradient or by a spin accumulation using Fermi's Golden Rule [3].

We find a sensitive dependence on the magnetic order as well as on the interface parameters.

[1] Wang et al., Phys. Rev. Lett. 113, 097202 (2014), Phys. Rev. B 91, 220410(R) (2015); Lin et al. Phys. Rev. Lett. 116, 186601 (2016).

[2] Khymyn et al., Phys. Rev. B 93, 224421 (2016); Rezende et al., Phys. Rev. B 93, 054412 (2016).

[3] Bender et al., Phys. Rev. Lett. 108, 246601 (2012).