Vacancy-induced spin textures and their interactions in a classical spin liquid

Sen, Arnab ; Damle, Kedar ; Moessner, R. (2012) Vacancy-induced spin textures and their interactions in a classical spin liquid Physical Review B: Condensed Matter and Materials Physics, 86 (20). Article ID 205134. ISSN 2469-9950

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Motivated by experiments on the archetypal frustrated magnet SrCr9pGa12−9pO19 (SCGO), we study the classical Heisenberg model on the pyrochlore slab (kagomé bilayer) lattice with site dilution x=1−p. This allows us to address generic aspects of the physics of nonmagnetic vacancies in a classical spin liquid. We explicitly demonstrate that the pure (x=0) system remains a spin liquid down to the lowest temperatures, with an unusual nonmonotonic temperature dependence of the susceptibility, which even turns diamagnetic for the apical spins between the two kagome layers. For x>0 but small, the low-temperature magnetic response of the system is most naturally described in terms of the properties of spatially extended spin textures that cloak an “orphan” S=3/2 Cr3+ spin in direct proximity to a pair of missing sites belonging to the same triangular simplex. In the T→0 limit, these orphan-texture complexes each carry a net magnetization that is exactly half the magnetic moment of an individual spin of the undiluted system. Furthermore, we demonstrate that they interact via an entropic temperature-dependent pairwise exchange interaction Jeff(T,⃗r)∼TJ(⃗r√T) that has a logarithmic form at short distances and decays exponentially beyond a thermal correlation length ξ(T)∼1/√T. The sign of Jeff depends on whether the two orphan spins belong to the same kagome layer or not. We provide a detailed analytical account of these properties using an effective field theory approach specifically tailored for the problem at hand. These results are in quantitative agreement with large-scale Monte Carlo numerics.

Item Type:Article
Source:Copyright of this article belongs to American Physical Society.
ID Code:103882
Deposited On:09 Mar 2018 11:31
Last Modified:09 Mar 2018 11:31

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