Large magnetoelectric effects mediated by electric-field-driven nanoscale phase transformations in sputtered (nanoparticulate) and electrochemically dealloyed (nanoporous) Fe-Cu films.

Shauna Robbennolt,Eva Pellicer,Alberto Quintana,Jordi Sort

doi:10.1039/c8nr03924k

Abstract

Large magnetoelectric effects are observed in as-sputtered (nanoparticulate-like) and electrochemically dealloyed (nanoporous) 200 nm thick Fe-Cu films. Application of positive voltages decreases both the saturation magnetization (MS) and coercivity (HC) of the films, while negative voltages cause the reverse effect (increase of MS and HC). The relative variations are as high as 20% for MS and beyond 100% for HC, both for the as-sputtered and dealloyed states. These changes in magnetic properties are caused by controlled and reversible electric-field-driven nanoscale phase transformations between face-centered cubic (fcc) and body-centered cubic (bcc) structures. These phase transitions are in turn due to selective redox reactions induced by the applied voltage, which can be regarded as a "magnetoionic effect." The controlled tuning of HC and MS with the moderate values of applied voltage, together with the sustainable composition of the investigated alloys (not containing noble metals, as opposed to many previous works on magnetoelectric effects in thin films), pave the way towards the implementation of magnetic and spintronic devices with enhanced energy efficiency and functionalities.

Highlights

Voltage control of magnetism is an exciting area of research due to the increasing demand to create smaller and more energy-efficient spintronic devices
The small cylindrical cell was mounted to a Vibrating Sample Magnetometer (VSM) sample holder and placed in the instrument – the magnetic field coils shown here
We have reported on the control of magnetism by applied voltage in Fe–Cu thin films

Summary

Introduction

Voltage control of magnetism is an exciting area of research due to the increasing demand to create smaller and more energy-efficient spintronic devices. We investigate the effects of an in situ applied voltage on the magnetic properties of nanoparticulate and nanoporous Fe–Cu thin films. The magnetic properties of both the as-sputtered and dealloyed films are investigated as a function of applied voltage.

Results

Conclusion