Magnetic-electric behaviors in BiFeO3 films grown on LaNiO3-buffered Si substrate

BiFeO3 films with different thicknesses and crystallographic orientations were grown on LaNiO3-buffered Si substrates via a modified chemical route. Remarkable size effect in ferroelectric behavior was observed with thicker films exhibiting a larger polarization value, due to combined depolarization effect and microstructure of the BiFeO3 films. High resolution transmission electron micrograph revealed a complex strain state in the BiFeO3 films, and the net magnetic moment induced by the canting of the antiparallel spins was arranged in disorder in thicker films, presenting a spin-glass state; while in the thinner BiFeO3 films, the disorder spins turned to be orderly arranged to induce a ferromagnetic behavior. Thus there exists a competition between ferroelectric and magnetic behaviors as film thickness changes. Furthermore, magnetoelectric coupling was observed in the BiFeO3 films with a magnetic-field-induced electrical voltage of around 3.5 μV/Oe.