NMR evidence against a spin-nematic nature of the presaturation phase in the frustrated magnet SrZnVO(PO4)2

Abstract

Using P31 nuclear magnetic resonance (NMR) we investigate the recently discovered presaturation phase in the highly frustrated two-dimensional spin system SrZnVO(PO4)2 [F. Landolt, Phys. Rev. B 104, 224435 (2021)10.1103/PhysRevB.104.224435]. Our data provide two pieces of evidence against the presumed spin-nematic character of this phase: (i) NMR spectra reveal that it hosts a dipolar spin order and (ii) the T1-1 relaxation rate data recorded above the saturation field can be fitted by the sum of a single-magnon term, exponential in the gap, and a critical second-order term, exponential in the triple gap, leaving no space for a nematic spin dynamics, characterized by a double-gap exponential. We explain the unexpectedly broad validity of the simple fit and the related critical spin dynamics.