We report neutron scattering and AC magnetic susceptibility measurements of the 2D spin-1/2 frustrated magnet BaCdVO(PO4)2. At temperatures well below TN≈1K, we show that only 34 % of the spin moment orders in an up-up-down-down strip structure. Dominant magnetic diffuse scattering and comparison to published μsr measurements indicates that the remaining 66 % is fluctuating. This demonstrates the presence of strong frustration, associated with competing ferromagnetic and antiferromagnetic interactions, and points to a subtle ordering mechanism driven by magnon interactions. On applying magnetic field, we find that at T=0.1 K the magnetic order vanishes at 3.8 T, whereas magnetic saturation is reached only above 4.5 T. We argue that the putative high-field phase is a realization of the long-sought bond-spin-nematic state.
@article{arxiv.1903.12462,
title = {Putative spin-nematic phase in BaCdVO(PO$_{4}$)$_{2}$},
author = {M. Skoulatos and F. Rucker and G. J. Nilsen and A. Bertin and E. Pomjakushina and J. Ollivier and A. Schneidewind and R. Georgii and O. Zaharko and L. Keller and Ch. Rüegg and C. Pfleiderer and B. Schmidt and N. Shannon and A. Kriele and A. Senyshyn and A. Smerald},
journal= {arXiv preprint arXiv:1903.12462},
year = {2019}
}