Thermal capacity,diffusion, and conductivity of Nd1−xSrxMno3 (x = 0.45 and 0.5) manganites

Temperature dependences (77–300 K) of the thermal capacity, diffusion, and conductivity are investigated for the Nd _0.5 Sr _0.5 MnO ₃ and Nd _0.55 Sr _0.45 MnO ₃ polycrystalline samples. The examined characteristics show anomalous behavior in the magnetic phase transition and transition to the charge-ordered state. It is demonstrated that the main reason for a sharp decrease in the thermal conductivity during Nd _0.5 Sr _0.5 MnO ₃ transition into the antiferromagnetic charge-ordered state is a change in the phonon spectrum caused by the lattice compression. A temperature dependence of the free phonon path is calculated for the examined temperature interval based on the thermal diffusion obtained and the literature data on the sound propagation velocity. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 72–75, April, 2007.