Structural and magnetoelectric properties of Ga_(2-x)Fe_xO_3 single crystals grown by a floating-zone method

摘要

Lattice-structural, magnetic, and magnetoelectric (ME) properties have been investigated for single crystals of prototypical polar ferrimagnet Ga_(2-x)Fe_xO_3 (0.8 ≤ x ≤ 1.4) as melt-grown by a floating-zone (FZ) method. Magnetization measurements show that the saturated magnetization as well as the ferrimagnetic phase transition temperature (T_C) increases with as increase of Fe content x, while the coercive force decreases. A neutron powder diffraction study indicates fairly low ordering of Ga and Fe arrangement at cation sites, which is likely related to the lower T_C in the FZ crystals than in the corresponding flux-grown crystals. Coefficients of linear and quadratic ME effects have been obtained with measurements of change in electric polarization induced by sweeping a magnetic field. Electric polarization was largely modulated in a magnetic field applied parallel to the direction of spontaneous magnetization, but not in a field parallel to that of the spontaneous polarization. A simple model to explain the sharp contrast is presented.