Room Temperature Ferromagnetism with Large Magnetic Moment at Low Field in Rare-Earth-doped BiFeO3 Thin Films

Abstract

BiFeO3 is a promising multiferroic material due to its high ferroelectric (1103 K) and antiferromagnetic (643 K) ordering temperatures. Previous reports have suggested that by reducing the dimensionality, the spiral magnetic ordering could be suppressed

therefore, the magnetic properties could be modified. In BiFeO3, if Bi is partially substituted by a small amount of divalent or trivalent metal ions, or Fe is substituted by transition metal ion, a significant enhancement in magnetization can be achieved. Thin films of Rare Earth (Re) - doped BiFeO3 (where RE = Sm, Ho, Pr and Nd) were grown on LaAlO3 substrates by using pulsed laser deposition technique. All the films show a single phase of rhombohderal structure with space group R3c. The saturated magnetization in the Ho- and Sm- doped films is much larger than those reported in literature, and was observed at a quite low field as of 0.2 T. In the case of Ho and Sm doping, the magnetization increases when the film becomes thinner, suggesting that the observed magnetism is mostly due to surface effect. In the case of Nd doping, even though the thin film has large magnetic moment, the mechanism seems to be different.