Transformation of spin current by antiferromagnetic insulators

TL;DR

This paper theoretically demonstrates how a thin anisotropic antiferromagnetic insulator can transfer and modify spin currents via evanescent spin wave modes, with effects influenced by temperature and layer thickness.

Contribution

It introduces a theoretical model showing spin current transformation and enhancement through AFM insulators, highlighting the role of evanescent modes and temperature dependence.

Findings

Maximum spin current transfer occurs at an optimal AFM thickness.

Spin current can be significantly amplified, exceeding input magnitude.

Transfer efficiency increases near the Neel temperature.

Abstract

It is demonstrated theoretically that a thin layer of an anisotropic antiferromagnetic (AFM) insulator can effectively conduct spin current by excitation of a pair of evanescent AFM spin wave modes. The spin current flowing through the AFM is not conserved due to the interaction between the excited AFM modes and the AFM lattice, and, depending on the excitation conditions, can be either attenuated or enhanced. When the phase difference between the excited evanescent modes is close to $\pi/2$, there is an optimum AFM thickness for which the output spin current reaches a maximum, that can significantly exceed the magnitude of the input spin current. The spin current transfer through the AFM depends on the ambient temperature and increases substantially when temperature approaches the Neel temperature of the AFM layer.