Spin transfer and spin pumping in disordered normal metal-antiferromagnetic insulator systems

TL;DR

This paper investigates how disorder and spin-flip scattering in metals affect spin transfer and spin pumping in antiferromagnetic insulator-metal systems, revealing the decay and non-conservation of staggered spin currents.

Contribution

It provides a detailed analysis of the impact of disorder and spin-flip processes on spin transfer torques and spin currents in antiferromagnet-metal interfaces, introducing a network model for decay.

Findings

Spin-independent disorder reduces spin coupling similar to Ohm's law.

Spin-flip scattering causes spin-memory loss and reduces spin-transfer torque.

Staggered spin current is not conserved and decays rapidly away from the interface.

Abstract

We consider an antiferromagnetic insulator that is in contact with a metal. Spin accumulation in the metal can induce spin-transfer torques on the staggered field and on the magnetization in the antiferromagnet. These torques relate to spin pumping: the emission of spin currents into the metal by a precessing antiferromagnet. We investigate how the various components of the spin-transfer torque are affected by spin-independent disorder and spin-flip scattering in the metal. Spin-conserving disorder reduces the coupling between the spins in the antiferromagnet and the itinerant spins in the metal in a manner similar to Ohm's law. Spin-flip scattering leads to spin-memory loss with a reduced spin-transfer torque. We discuss the concept of a staggered spin current and argue that it is not a conserved quantity. Away from the interface, the staggered spin current varies around a zero mean in an irregular manner. A network model explains the rapid decay of the staggered spin current.