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Observation of Kosterlitz-Thouless spin correlations in the colossally magnetoresistive layered manganite $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$

S. Rosenkranz·R. Osborn·L. Vasiliu-Doloc·J. W. Lynn·S. K. Sinha·J. F. Mitchell
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Abstract

The spin correlations of the bilayer manganite $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$ have been studied using neutron scattering. On cooling within the paramagnetic state, we observe purely two-dimensional behavior with a crossover to three-dimensional scaling close to the ferromagnetic transition. Below $T_C$, an effective finite size behavior is observed. The quantitative agreement of these observations with the conventional quasi two-dimensional Kosterlitz-Thouless model indicates that the phase transition is driven by the growth of magnetic correlations, which are only weakly coupled to polarons above $T_C$.

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S. Rosenkranz, R. Osborn, L. Vasiliu-Doloc, J. W. Lynn, S. K. Sinha, J. F. Mitchell. 1999-09-03. Observation of Kosterlitz-Thouless spin correlations in the colossally magnetoresistive layered manganite $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$. https://arxiv.org/abs/cond-mat/9909059

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