Jensen, T B SChristensen, N BKenzelmann, MRonnow, H MNiedermayer, CAndersen, N HLefmann, KSchefer, JVon Zimmermann, MLi, JZarestky, J LVaknin, D2010-02-082010-02-082010-02-08200910.1103/PhysRevB.79.092412https://infoscience.epfl.ch/handle/20.500.14299/46495WOS:000264768200015Neutron diffraction is used to probe the (H,T) phase diagram of magnetoelectric (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 k(C)=(0,0,0); the other one is incommensurate (IC) with k(IC)=(0,q,0). At low temperatures the C order collapses above mu H-0=12 T and adopts an IC structure with modulation vector parallel to k(IC). 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.antiferromagnetismlithium compoundsmagnetic structuremagnetic transitionsmagnetoelastic effectsmagnetoelectric effectsneutron diffractionnickel compoundstext::journal::journal article::research article