Abstract
Neutron diffraction is used to probe the phase diagram of magnetoelectric (ME) for magnetic fields along the axis. At zero field the Ni spins order in two antiferromagnetic phases. One has commensurate (C) structures and general ordering vectors ; the other one is incommensurate (IC) with . At low temperatures the C order collapses above and adopts an IC structure with modulation vector parallel to . We show that C order is required for the ME effect and establish how electric polarization results from a field-induced reduction in the total magnetoelastic energy.
- Received 11 November 2008
DOI:https://doi.org/10.1103/PhysRevB.79.092412
©2009 American Physical Society