Photoacoustic study on phase transitions in La1-xCaxMnO3 (x=0.2, 0.3, 0.4)

The phase transitions in the manganite perovskite compounds La_1-xCa_xMnO₃ (x=0.2, 0.3, 0.4) have been studied using magnetization, resistivity, and photoacoustic measurements. The phase transition temperatures determined from the anomaly of the photoacoustic signal are consistent with those determined from the magnetization measurements. For x=0.3, the paramagnetic to ferromagnetic phase transition can be regarded as a second order phase transition with no latent heat at the phase transition temperature. The relative value of the multiplication of specific heat and thermal conductivity can be obtained from the photoacoustic signal using Rosencwaig and Gersho´s theory,