Exchange bias in room-temperature epitaxial Fe3O4 film

• Exchange bias effect is observed in room-temperature epitaxial Fe3O4 film.
• Training effect of exchange bias in the Fe3O4 film is observed.
• Exchange bias field and coercivity field decrease with increasing temperature.

We have grown 100-nm-thick epitaxial Fe3O4(111) film on α-Al2O3(0001) substrate at room temperature by the laser molecule beam epitaxy method. Exchange bias effect is observed once the film is cooled from 300 K to 5 K in the presence of a magnetic field, characterized by the shift and expansion of magnetic hysteresis loops. The observed exchange bias effect is related to the exchange coupling between antiferromagnetic Fe–O–Fe superexchange interactions at antiphase domain boundaries and ferromagnetic spins in the neighboring Fe3O4 domains. The magnitudes of the exchange bias field and coercive field show strong dependence on magnetic and thermal histories.