Thermally-controlled interlayer exchange and field-induced anisotropy in synthetic antiferromagnets

TL;DR

This paper demonstrates thermally-controlled interlayer exchange and field-induced anisotropy in synthetic antiferromagnets, revealing temperature-dependent magnetic alignment and a field-induced uniaxial anisotropy resembling a metamagnet.

Contribution

It introduces a method to control interlayer exchange in synthetic antiferromagnets via temperature, highlighting the role of a paramagnetic spacer in tuning magnetic states.

Findings

Interlayer exchange can be thermally controlled in multilayers.

The spacer's magnetic polarization affects coupling at different temperatures.

Field-induced uniaxial anisotropy is observed despite lack of intrinsic anisotropy.

Abstract

Interlayer exchange in synthetic antiferromagnets incorporating thin paramagnetic spacers can be controlled thermally. The spacer provides an additional ferromagnetic contribution that renormalizes the otherwise temperature-independent interlayer coupling. As a result, the system shows antiferromagnetic alignment at high temperatures and ferromagnetic alignment at low temperatures. This behavior is observed in Fe(2 nm)/Cr(0.4 nm)/Fe$_{17.5}$Cr$_{82.5}$(0.9 nm)/Cr(0.4 nm)/Fe(2 nm) multilayers with the inner spacer Fe$_{17.5}$Cr$_{82.5}$ paramagnetic at and above room temperature, and is shown to be due to the spacer being significantly magnetically polarized on lowering the temperature toward its Curie point. Although the Fe layers lack intrinsic magnetocrystalline anisotropy, the magnetization reversal demonstrates a field-induced uniaxial anisotropy of antiferromagnetic character. The resulting reversal process resembles that of a metamagnet with a spin-flip transition.