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TT: Fachverband Tiefe Temperaturen

TT 38: Correlated Electrons: Spin Systems and Itinerant Magnets 1

TT 38.2: Vortrag

Donnerstag, 29. März 2012, 09:45–10:00, H 3010

Non-magnetic impurities in a classical spin liquid — •Arnab Sen¹, Kedar Damle², and Roderich Moessner¹ — ¹Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany — ²Tata Institute of Fundamental Research, Mumbai, India

Impurities can potentially reveal the underlying correlations in spin liquid states that appear deceptively featureless in their ground state properties. We consider the archetypal frustrated antiferromagnet SrCr_9pGa_12−9pO₁₉ (SCGO) in which Ga ions act as non-magnetic impurities in the magnetic lattice composed of Cr³⁺ S=3/2 spins for disordered p<1 samples. We show that a spin in direct proximity to a pair of vacancies 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. We calculate the full texture on the lattice in the spin liquid regime and check that it agrees well with Monte-Carlo (MC) simulations. This texture leaves an unmistakable imprint on the measured ⁷¹Ga NMR lineshapes, which we compute using MC simulations and compare with experimental data. These spin-textures have long range interactions with each other in the spin liquid regime. We show how these interactions can be understood in a simple manner from our analytic theory, and support the predictions using numerical simulations.