Exchange bias and vertical shift of the magnetic hysteresis loop in Co/BiFeO3 bilayers

Abstract

To reveal the mechanism of interfacial exchange coupling, the magnetic hysteresis (M-H) loop of Co/BiFeO3 bilayers deposited on (001) LaAlO3 (LAO) substrates by magnetron sputtering was measured. The M-H loop displays a horizontal shift along the field axis coexisting with a vertical shift along the magnetization axis. The frozen uncompensated interfacial spins result in the EB effect, as demonstrated by the similar dependencies between EB and the vertical shift in temperature and BFO thickness. In addition, the M-H loop also shows an enhancement in magnetization, which is considered to result from the induced net moments at the interface.