Multiferroic Properties of Bi0.9Gd0.1Fe0.9Mn0.1O3 Thin Film

Monolithic oxides whose lattice structures exhibit both ferroelectric and magnetic ordering and eventually intrinsic coupling between them are known as multiferroics. The possibility to switch magnetization by an electric field and reciprocally polarization by a magnetic field may allow new applications spanning the fields from new memory devices to medical measuring technology. Until now, the only monolithic oxide that has been shown to exhibit both (weak) magnetism and ferroelectric polarization at room temperature is BiFeO3 (BFO). However, as this material is a line compound, i.e., with sharply defined stoichiometry, its properties largely depend on defects and parasitic phases that could arise during processing. In the present work, we report on a new compound based on the solid solution GdMnO3–BiFeO3 (GdMBFO) that exhibit a fairly high magnetization coupled with moderate ferroelectric polarization at room temperature. Using conductive-tip atomic force microscopy, we show the highly electrically homogeneous microstructure. Ferroelectric polarization switching is obtained both as P-E hysteresis (or I-E) and capacitance-voltage butterfly curves. The effects of space charge on ferroelectric polarization that often bias polarization measurements reported for pure BFO are shown to be marginal. The high magnetization obtained for GdMBFO has allowed us to determine the Néel temperature (TN) directly from magnetic measurements. This results bears novelty as it is the first time that TN is reported for BFO-base thin films. The origin of magnetization improvement is discussed in terms of Gd substitution effects on octahedral distortion and tilting.