Re-entrant spiral magnetic order and ferroelectricity in Mn(1-x)FexWO(4) (x=0.035)

We report the observation of a re-entrant spiral (noncollinear) magnetic order and ferroelectricity below 6 K in Mn0.965Fe0.035WO4 under applied magnetic fields above 3.6 T. At zero field, this compound shows a transition into the spiral magnetic and ferroelectric phase at 12 K, and it becomes paraelectric at 10.5 K with the entrance into the commensurate magnetic phase, which is the ground state at H=0. Under magnetic field above 3.6 T, however, the spiral magnetic phases with a larger FE polarization reappears below 6 K. The re-entrant magnetic/ferroelectric phase behavior is further studied by single crystal neutron scattering and the H-T phase diagram is completely resolved from neutron, dielectric constant, polarization, and magnetic measurements. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3079865