Heat capacity of La1−xSrxMnO3 single crystals in different magnetic states

Abstract

The heat capacity of three single-crystal samples of La 1− x Sr x MnO 3 ( x =0, 0.2, and 0.3) is measured in the temperature range 4–400 K. It is found that the heat capacity undergoes abrupt changes due to the transitions from the antiferromagnetic phase to the paramagnetic phase ( x =0) and from the ferromagnetic phase to the paramagnetic phase ( x =0.2 and 0.3). The phonon contribution to the heat capacity and the Debye characteristic temperatures for the La 0.7 Sr 0.3 MnO 3 sample are determined over a wide range of temperatures. The electronic density of states at the Fermi level is evaluated. It is demonstrated that an increase in the strontium concentration x brings about an increase in the electronic density of states at the Fermi level. The contributions of spin waves to the heat capacity and the entropy are estimated under the assumption that the phonon spectrum remains unchanged upon doping with Sr.