Magnetic phase transition of Pr0.5Sr0.5-xCaxCoO3

Electrical and magnetic measurements have been carried out on Pr0.5Sr0.5-xCaxCoO3 (0 <= X <= 0.5). For x = 0.0, the system shows metallic/ferromagnetic behavior and the Curie temperature T, has been detected at T = 230 K. Upon increasing the Ca concentration (x), the system becomes weak insulator/ferromagnetic with rather small magnetic moment and the transition temperature is shifted to lower temperature, down to 80 K for x = 0.5. The same phase transition has been detected in the resistivity-temperature curves for these systems. The magnetic phase diagram for the Pr0.5Sr0.5-xCaxCoO3 system has been constructed, based on the experimental results. The experimental data can be well understood from the relationship between the ionic radii of Sr and Ca, as well as from the energy difference of spin states in the low-temperature region.