Effects of the Cu Doping on Critical Behavior of La0.7Ca0.3MnO3
We have studied the influence of the Cu-doping on the critical properties of a polycrystalline sample of La0.7Ca0.3Mn0.95Cu0.05O3 prepared by solid-state reaction. Analyses of static magnetization data in the vicinity of the ferromagnetic-paramagnetic phase transition based on the modified Arrott plot reveal critical parameters of T-C approximate to 197.3 K , beta = 0.49 +/- 0.03 and gamma = 1.04 +/- 0.04. These parameters are in good agreement with a magnetic equation of state M(H, epsilon) = epsilon(beta)f(+/-)(H/epsilon(beta+gamma)), where epsilon = (T - T-C)/T-C (the reduced temperature), f(+) for T > T-C and f(-) for T < T-C. Comparing with theoretical models, the critical exponents in our case are close to those expected for the mean-field theory. This reflects that the Cu doping leads to the second-order phase transition in La(0.7)Ca(0.3)Mn(0.95)Cu(0.05)O3 while the parent compound of La0.7Ca0.3MnO exhibits the first-order phase transition. Such the phenomeno...