Electronic transport and magnetic properties of La1-xCaxMnO3 (0 < x ≤ 1)

Abstract

We investigate the electronic transport and magnetic properties of La1-xCaxMnO3 across a wide range of calcium doping (x = 1/8, 1/4, 1/3, 1/2, 2/3, 3/4, and 1), unveiling distinct electronic and magnetic phase transitions. The findings can be summarized as follows. For samples with x = 1/8, 1/4, and 1/3, a transition temperature is observed at 188 K, 240 K, and 270 K, respectively. The x = 1/2 sample exhibits a charge ordering state, showing thermal hysteresis in electrical resistivity, thermopower, and magnetization. For samples with x = 2/3 and 3/4, a charge ordering state is observed at temperatures of 260 K and 225 K, respectively. However, there is no evidence of thermal hysteresis in terms of electrical resistivity, thermopower, and magnetization. Electrical resistivity and thermopower measurements follow the small polaron hopping model for x = 1/8, 1/4 and 1/3, while the variable range hopping model is applicable for x = 2/3, 3/4, and 1 at high temperatures. The sign and magnitude of the thermopower are found to be dependent on the calcium content. For samples with x less than 1/3, the thermopower is positive. In the case of the sample where x = 1/3, the thermopower changes sign, shifting from negative to positive below 101.8 K. Samples with x greater than 1/3 exhibit negative thermopower. The magnetization curves exhibit a decrease near the magnetic transition temperatures, specifically at 240 K for the x = 1/4 sample and 270 K for the x = 1/3 sample.