Magnetoelectric effect and magnetic phase transitions in (FexCr1-x)2O3 single crystals

The magnetoelectric effect in (FexCr1-x)(2)O-3 (x=0, 0.02, 0.05, 0.1) single crystals has been studied under a magnetic field of up to 200 kOe. We have found that various magnetic phase transitions due to the restructuring of the spatial spin structure and leading to radical changes in the magnetoelectric effect take place in substitutional alloys. We have also detected a spontaneous phase transition from a conical helix to a cycloidal spin structure laking place at x = 0.1 and a temperature of 45 K. The experimental data are in agreement with the theoretical concept based on the thermodynamic model and can be accounted for in terms of competition among exchange energies of different modes.