Room Temperature Exchange Bias in BiFeO3/Co-Fe Bilayers

Sterwerf C, Meinert M, Arenholz E, Schmalhorst J-M, Reiss G. Room Temperature Exchange Bias in BiFeO3/Co-Fe Bilayers. IEEE Transactions on Magnetics. 2016;52(7): 4800204.Thin highly epitaxial BiFeO3 films were prepared on SrTiO3 (100) substrates by reactive magnetron cosputtering. Detailed magneto-optic Kerr effect (MOKE) measurements on BiFeO3/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 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. Anisotropic magnetoresistance measurements reveal a strongly increasing coercivity with decreasing temperature, but no significant change in the exchange bias field