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

Using $³¹\mathrm{P}$ nuclear magnetic resonance (NMR) we investigate the recently discovered presaturation phase in the highly frustrated two-dimensional spin system $\mathrm{SrZnVO}{({\mathrm{PO}}₄)}₂$ [F. Landolt et al., Phys. Rev. B 104, 224435 (2021)]. 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 ${T}₁^{\ensuremath{-}1}$ 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.