Critical exponents of the La0.7Sr0.3MnO3, La0.7Ca0.3MnO3, and Pr0.7Ca0.3MnO3 systems showing correlation between transport and magnetic properties -: art. no. 103903

From the low-temperature (down to 10 K) dc-magnetization data of the La0.7Sr0.3MnO3 (LSM), La0.7Ca0.3MnO3 (LCM), and Pr0.7Ca0.3MnO3 (PCM) systems, we estimated the critical exponents beta, gamma, and hence delta from the analysis of the modified Arrot plots. The exponent beta estimated for the LCM system is less than that predicted by Heisenberg model and resides within the zone predicted by Ising model while for the LSM sample, beta is higher than that predicted from the Heisenberg model which is considered to be due to the presence of dipole-dipole interaction arising from the large spin moment in the LSM system. The magnetization data of the PCM system cannot be fitted to the modified Arrot plots, which suggest highly inhomogeneous ground state even under 5 T magnetic field. Both LSM and LCM have almost equal values of gamma. Seebeck coefficient data indicate a crossover from higher-temperature n-type to lower-temperature p-type conductivity behavior in both LSM and LCM systems, while the semiconducting PCM system shows p-type conductivity throughout the temperature range (300-80 K). It is noticed that for LSM system T-C (Curie temperature) and T-MI (metal-insulator transition temperature) are almost equal (similar to 360 K), whereas for the LCM system there exist a large difference between T-C and T-MI (T-C similar to 245 K and T-MI similar to 265 K), which may give some idea regarding the critical behavior of the respective samples. (c) 2005 American Institute of Physics.