Structural, magnetic, dielectric properties of multiferroic GaFeO3 prepared by solid state reaction and sol-gel methods

Polycrystalline GaFeO3 prepared by a solid state (SR) and a sol-gel (SG) procedure crystallize in the orthorhombic system with space group Pc2(1) n. Neutron powder diffraction revealed iron ions fractions over the four sites Ga1, Ga2, Fe1 and Fe2: (0.2, 0.55, 0.70, 0.55) and (0.04, 0.75, 0.51, 0.72) for GaFeO3 (SR) and GaFeO3 (SG), respectively. The Curie temperature (T-C) for GaFeO3 (SR) is about 190 K and increases to room temperature when the temperature of annealing is decreased from 1400 to 900 C. The dielectric constant and dielectric loss are temperature and frequency independent for both samples. Below the transition temperature, T-C, a ferrimagnetic order with a propagation vector k = 0 was derived from neutron powder diffraction data. The Fe3+ magnetic moments are ordered along the c-axis with a small component along a and b. At 3 K, the magnetic moments of Fe3+ are 3.47(9) and 4.40(1)mu(B) for GaFeO3 (SR) and GaFeO3 (SG), respectively. Both, the cation and magnetic ordering depend strongly on the preparation conditions. (C) 2009 Elsevier B.V. All rights reserved.