Narrowly avoided spin-nematic phase in BaCdVO(PO4)2: NMR evidence

Abstract

We present a P31 NMR investigation of BaCdVO(PO4)2 focusing on the nearly saturated regime between μ0Hc1=4.05T and μ0Hc2=6.5T, which used to be considered a promising candidate for a spin-nematic phase. NMR spectra establish the absence of any dipolar order there, whereas the weak field dependence of the magnetization above Hc1 is accounted for by Dzyaloshinskii-Moriya interaction terms. The low-energy spin dynamics (fluctuations), measured by the nuclear spin-lattice relaxation rate T1−1, confirms the continuity of this phase and the absence of any low-temperature phase transition. Unexpectedly, the spin dynamics above Hc1 is largely dominated by two-magnon processes, which is expected the saturation field of a spin-nematic phase, but not inside. This shows that BaCdVO(PO4)2 is indeed close to a spin-nematic instability; however, this phase is stabilized. We thus confirm recent theoretical predictions that the spin-nematic phase can be stabilized, at most, in an extremely narrow field range close to saturation or is rather narrowly avoided [Jiang , ]. Published by the American Physical Society 2024