Exponential Dependence of Interlayer Exchange Coupling in Fe/MgO(001) Superlattices on Temperature

TL;DR

This study reveals that interlayer exchange coupling in Fe/MgO(001) superlattices exponentially increases as temperature decreases, leading to a transition from antiferromagnetic to orthogonal magnetic alignment around 150 K due to quantum well states.

Contribution

It demonstrates the exponential temperature dependence of exchange coupling and identifies a magnetic ground state transition linked to quantum well states in Fe/MgO superlattices.

Findings

Exchange coupling increases exponentially with decreasing temperature.

Transition from discrete switching to collective rotation at ~150 K.

Magnetic ground state changes from 180° to 90° alignment.

Abstract

The interlayer exchange coupling in Fe/MgO(001) superlattices is found to increase exponentially with decreasing temperature. Around 150~K, the field induced response changes from discrete switching, governed by field-driven domain propagation, to a collective rotation of the magnetic layers. This transition is accompanied by a change in the magnetic ground state from 180$^{\circ}$ (antiferromagnetic) to 90$^{\circ}$ alignment between adjacent Fe layers. These effects are argued to arise from quantum well states, defined by the total thickness of the samples.