Abstract
A flop of electric polarization from to is observed in as a spin-flop transition is triggered by a -axis magnetic field, T. The critical magnetic field for is significantly reduced in . and have been observed with both and . Neutron diffraction measurements revealed similar magnetic arrangements for the two compositions where the ordered spins couple antiferromagnetically with their nearest intra- and interplanar neighbors. In the system, the uniaxial and planar anisotropies of and compete and give rise to a spin reorientation transition at . A magnetic field, , aligns the spins along for . The rotation of the collinear spins away from the axis for alters the magnetic point symmetry and gives rise to a new magnetoelectric (ME) susceptibility tensor form. Such linear ME response provides a satisfactory explanation for the behavior of the field-induced electric polarization in both compositions. As the Ni content increases to and 0.68, the ME effect disappears as a new magnetic phase emerges.
- Received 13 January 2014
- Revised 28 July 2014
DOI:https://doi.org/10.1103/PhysRevB.90.144429
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