Probing structural inhomogeneities induced by exchange striction above TN in antiferromagnetic perovskites

Measurements of the temperature dependence of the thermal conductivity κ(T) of the antiferromagnetic perovskites SmNiO 3 , CaMnO 3 , LaMnO 3 , and YCrO 3 are compared to that of the nonmagnetic perovskite LaGaO 3 . Whereas LaGaO 3 exhibits a classic phonon thermal conductivity, the others all show a remarkable suppression of K(T) in the paramagnetic phase that increases with the degree of covalence in the M-O bond. This suppression is attributed to exchange-strictive fluctuations that are enhanced by semicovalent-exchange interactions.

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