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

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.

4 pages, 2-column format, 3 color figures