Spin transport across antiferromagnets induced by the spin Seebeck effect

TL;DR

This paper provides a theoretical and experimental analysis of magnonic spin current transport across antiferromagnets induced by the spin Seebeck effect, highlighting the transfer of angular momentum and phase transition effects.

Contribution

It offers a detailed atomistic simulation study and experimental validation of spin transport in ferromagnetic-antiferromagnetic multilayers, focusing on IrMn and YIG heterostructures.

Findings

Magnonic spin transport length scales in antiferromagnets are identified.

Angular momentum transfer occurs via excitation of a single magnon branch.

Spin transport signals depend on temperature and thickness, linked to phase transitions.

Abstract

For prospective spintronics devices based on the propagation of pure spin currents, antiferromagnets are an interesting class of materials that potentially entail a number of advantages as compared to ferromagnets. Here, we present a detailed theoretical study of magnonic spin current transport in ferromagnetic-antiferromagnetic multilayers by using atomistic spin dynamics simulations. The relevant length scales of magnonic spin transport in antiferromagnets are determined. We demonstrate the transfer of angular momentum from a ferromagnet into an antiferromagnet due to the excitation of only one magnon branch in the antiferromagnet. As an experimental system, we ascertain the transport across an antiferromagnet in YIG$|$Ir$_{20}$Mn$_{80}|$Pt heterostructures. We determine the spin transport signals for spin currents generated in the YIG by the spin Seebeck effect and compare to measurements of the spin Hall magnetoresistance in the heterostructure stack. By means of temperature-dependent and thickness-dependent measurements, we deduce conclusions on the spin transport mechanism across IrMn and furthermore correlate it to its paramagnetic-antiferromagnetic phase transition.