Room Temperature Exchange Bias in BiFeO3/Co–Fe Bilayers

Thin highly epitaxial BiFeO
₃
films were prepared on SrTiO
₃
(100) substrates by reactive magnetron cosputtering. Detailed magneto-optic Kerr effect (MOKE) measurements on BiFeO
₃
/Co-Fe bilayers were performed to investigate the exchange bias as a function of film thicknesses and Co-Fe stoichiometries. We found a maximum exchange bias of H
_eb
= 92 Oe and a coercive field of H
_c
= 89 O
_e
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. Anisotropic magnetoresistance measurements reveal a strongly increasing coercivity with decreasing temperature, but no significant change in the exchange bias field.