Switching on superferromagnetism

TL;DR

This paper demonstrates local switching of superferromagnetism in a Fe thin film on BaTiO3, showing electric-field-induced strain can induce a transition from superparamagnetic to superferromagnetic states near room temperature.

Contribution

It introduces a method to electrically control superferromagnetism in a ferromagnetic/ferroelectric heterostructure, enabling potential low-power magnetic data storage applications.

Findings

Electric-field-induced strain switches magnetic states.

Superparamagnetic to superferromagnetic transition observed.

Critical temperature increases due to electric-field effects.

Abstract

Recent results in electric-field control of magnetism have paved the way for the design of alternative magnetic and spintronic devices with enhanced functionalities and low power consumption. Among the diversity of reported magnetoelectric effects, the possibility of switching on and off long-range ferromagnetic ordering close to room temperature stands out. Its binary character opens up the avenue for its implementation in magnetoelectric data storage devices. Here we show the possibility to locally switch on superferromagnetism in a wedge-shaped polycrystalline Fe thin film deposited on top of a ferroelectric and ferroelastic BaTiO3 substrate. A superparamagnetic to superferromagnetic transition is observed for confined regions for which a voltage applied to the ferroelectric substrate induces a sizable strain. We argue that electric-field-induced changes of magnetic anisotropy lead to an increase of the critical temperature separating the two regimes so that superparamagnetic regions develop collective long-range superferromagnetic behavior.