Effect of Cr-doping on thermal transport property in perovskite R0.7A0.3Mn1-x Cr x O3

The thermal conductivity k(T) of R0.7A0.3Mn1-x Cr x O3 (R=La, Nd; A=Ca, Sr) have been studied as a function of Cr content (x) ranging from 0.01 to 0.60. The Cr3+ ions substitution for Mn3+ ions causes the orbital defect of electrons, resulting in the volume shrinkage of lattice. The light doping of Cr strongly suppresses the thermal conductivity k over a wide range of temperature. On the contrary, for the heavily Cr doping samples, a clear rebound in k was observed at the higher temperature region studied, which is not consistent with a typical impurity effect on lattice thermal conductivity. These findings are discussed on the basis of the lattice distortion associated with the local Jahn-Teller effect through orbital-lattice coupling, and as well the spin-dependent scattering through spin-lattice interactions