High magnetic field induced phases and half-magnetization plateau in theS=1kagome compound Ni3V2O8

Abstract

We report on high magnetic field studies of magnetization, electric polarization, and specific heat on single crystals of Ni${}_{3}$V${}_{2}$O${}_{8}$, which is an $S$ $=$ 1 kagome compound. The magnetization process exhibits multistep magnetic transitions when the magnetic field is parallel to the magnetic easy axis. An apparent magnetization plateau was observed at half the height of the saturation magnetization ${M}_{\mathrm{s}}$ \ensuremath{\sim} 2.39\ensuremath{\mu}${}_{\mathrm{B}}$/Ni. In addition, the magnetization transitions at higher fields are quantized at 2/3, 3/4, and 8/9 of ${M}_{\mathrm{s}}$. These results are unusual for the one-third magnetization plateaus that theories have predicted for conventional kagome antiferromagnets. We find that the high magnetic field suppresses the spontaneous polarization, leading to a different high-field phase where the magnetic structure is collinear or coplanar with the underlying lattice. The resulting high-field phase diagram explores several magnetic phases and sheds light on recent experimental findings. Analytical arguments have been presented to discuss these high-field phases.