Propagation of Exchange Bias in CoFe/FeMn/CoFe Trilayers

TL;DR

This study investigates how exchange bias propagates in CoFe/FeMn/CoFe trilayers, showing that the order of layers and FeMn thickness significantly influence the exchange bias fields, indicating interfacial magnetic interactions.

Contribution

It demonstrates the propagation of exchange bias across interfaces in trilayers and how layer order and thickness affect magnetic properties, which is a novel insight.

Findings

Exchange bias depends on deposition order.

Symmetric trilayers enhance exchange bias fields.

Reducing FeMn thickness increases bias fields.

Abstract

CoFe/FeMn, FeMn/CoFe bilayers and CoFe/FeMn/CoFe trilayers were grown in magnetic field and at room temperature. The exchange bias field $H_{eb}$ depends strongly on the order of depositions and is much higher at CoFe/FeMn than at FeMn/CoFe interfaces. By combining the two bilayer structures into symmetric CoFe/FeMn($t_\mathrm{FeMn}$)/CoFe trilayers, $H_{eb}^t$ and $H_{eb}^b$ of the top and bottom CoFe layers, respectively, are both enhanced. Reducing $t_\mathrm{FeMn}$ of the trilayers also results in enhancements of both $H_{eb}^b$ and $H_{eb}^t$. These results evidence the propagation of exchange bias between the two CoFe/FeMn and FeMn/CoFe interfaces mediated by the FeMn antiferromagnetic order.