Probing structural inhomogeneities induced by exchange striction above TN in antiferromagnetic perovskites -: art. no. 052401

Measurements of the temperature dependence of the thermal conductivity kappa(T) of the antiferromagnetic perovskites SmNiO3, CaMnO3, LaMnO3, and YCrO3 are compared to that of the nonmagnetic perovskite LaGaO3. Whereas LaGaO3 exhibits a classic phonon thermal conductivity, the others all show a remarkable suppression of kappa(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.