Room temperature exchange bias in BiFeO3 / Co-Fe bilayers

TL;DR

This study demonstrates room temperature exchange bias in BiFeO3/Co-Fe bilayers, with detailed measurements showing how film thickness and composition influence magnetic properties, highlighting potential for spintronic applications.

Contribution

The paper reports the first observation of room temperature exchange bias in BiFeO3/Co-Fe bilayers and analyzes its dependence on film parameters.

Findings

Maximum exchange bias of 92 Oe observed.

Coercivity increases with decreasing temperature.

Unidirectional anisotropy confirmed by in-plane rotational measurements.

Abstract

Thin highly epitaxial BiFeO$_3$ films were prepared on SrTiO$_3$ (100) substrates by reactive magnetron co-sputtering. Detailed MOKE measurements on BiFeO$_3$/Co-Fe bilayers were performed to investigate the exchange bias as a function of the films thicknesses and Co-Fe stoichiometries. We found a maximum exchange bias of H$_{\mathrm{eb}}$=92 Oe and a coercive field of H$_{\mathrm{c}}$=89 Oe for a 12.5 nm thick BiFeO$_3$ film with a 2 nm thick Co layer. The unidirectional anisotropy is clearly visible in in-plane rotational MOKE measurements. AMR measurements reveal a strongly increasing coercivity with decreasing temperature, but no significant change in the exchange bias field.