Room Temperature Exchange Bias in BiFeO₃/Co–Fe Bilayers

Abstract

Thin highly epitaxial BiFeO3 films were prepared on SrTiO3 (100) substrates by reactive magnetron co-sputtering. Detailed MOKE measurements on BiFeO3/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 Heb = 92 Oe and a coercive field of Hc = 89 Oe for a 12.5 nm thick BiFeO3 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.

High-Quality Sputtered BiFeO3 for Ultrathin Epitaxial Films

“…Using magnetoelectric multiferroic materials is one of the prime candidates for controlling magnetization by an electric field. In particular, bismuth ferrite (BiFeO 3 ) is a promising multiferroic material because of its high antiferromagnetic Néel (370 °C) with Dzyaloshinskii–Moriya (DM) interaction and high ferroelectric Curie (830 °C) temperatures. , The antiferromagnetic/ferroelectric BiFeO 3 shows coupling between antiferromagnetic and ferroelectric domains, an exchange bias effect with the ferromagnetic layer, , and also magnetization reversal by an electric field . Further development of magnetoelectric devices and the preparation of high-quality BiFeO 3 epitaxial films and ultrathin films is crucial.…”