Fractional Spin Textures in the Frustrated Magnet SrCr9pGa12-9pO19

We consider the archetypal frustrated antiferromagnet SrCr9pGa12-9pO19 in its well-known spin-liquid state, and demonstrate that a Cr3+ 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, our analytic theory predicts that 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 Ga-71 nuclear magnetic resonance line shapes, which we compute using Monte Carlo simulations and compare with experimental data.