Neutron diffraction is used to probe the (H,T) phase diagram of magneto-electric (ME) LiNiPO4 for magnetic fields along the c-axis. At zero field the Ni spins order in two antiferromagnetic phases. One has commensurate (C) structures and general ordering vectors (0,0,0), the other one is incommensurate (IC) with ordering vector (0,q,0). At low temperatures the C order collapses above 12 Tesla and adopts an IC structure with modulation vector parallel to (0,q,0). We show that C order is required for the ME effect and establish how electric polarization results from a field-induced reduction of the total magneto-elastic energy.
@article{arxiv.0901.2238,
title = {Field-induced magnetic phases and electric polarization in LiNiPO4},
author = {T. B. S. Jensen and N. B. Christensen and M. Kenzelmann and H. M. Rønnow and C. Niedermayer and N. H. Andersen and K. Lefmann and J. Schefer and M. v. Zimmermann and J. Li and J. L. Zarestky and D. Vaknin},
journal= {arXiv preprint arXiv:0901.2238},
year = {2009}
}
Comments
5 pages, 4 figures, accepted for publication in Phys. Rev. B