Strong room temperature exchange bias in self-assembled BiFeO3–Fe3O4 nanocomposite heteroepitaxial films

Self-assembled, nanocomposite heteroepitaxial films of BiFeO3 + Fe3O4 (x BiFeO3 + (1 − x) Fe3O4), where x = 0.5 or 0.9, were grown on (011) SrTiO3. Depending on the value of x and on the film thickness, either exchange bias or exchange enhancement of coercivity was demonstrated. In epitaxially and highly strained (7%) films of 250 nm thickness, and for x = 0.9, exchange bias (HEB) values of 40 Oe and HEB/HC ratios of 0.5 were achieved. Most crucially, these effects were measured at room temperature, showing the high potential of chemically compatible BiFeO3 + Fe3O4 for achieving room temperature magnetoelectricity.