Fractional spin textures in the frustrated magnet SrCr$_{9p}$Ga$_{12-9p}$O$_{19}$

TL;DR

This paper investigates how vacancies in the frustrated magnet SrCr$_{9p}$Ga$_{12-9p}$O$_{19}$ create extended spin textures that mimic fractional spins, affecting NMR signals and revealing underlying spin-liquid correlations.

Contribution

It demonstrates that vacancies induce fractional spin textures in the spin-liquid state, linking local defects to global magnetic responses and NMR signatures.

Findings

Vacancies generate extended spin textures with fractional spin characteristics.

The spin textures produce a magnetic response equivalent to a spin of S/2 = 3/4.

Monte Carlo simulations match experimental NMR lineshapes, confirming the theoretical model.

Abstract

We consider the archetypal frustrated antiferromagnet SrCr$_{9p}$Ga$_{12-9p}$O$_{19}$ in its well-known spin-liquid state, and demonstrate that a Cr$^{3+}$ spin $S=3/2$ ion in direct proximity to a pair of vacancies (in disordered $p<1$ samples) is cloaked by a spatially extended spin texture that encodes the correlations of the parent spin-liquid. In this spin-liquid regime, the combined object has a magnetic response identical to a classical spin of length $S/2 = 3/4$, which dominates over the small intrinsic susceptibility of the pure system. This fractional-spin texture leaves an unmistakable imprint on the measured $^{71}$Ga nuclear magnetic resonance (NMR) lineshapes, which we compute using Monte-Carlo simulations and compare with experimental data.