First-order-like magnetic transition in manganite oxide La0.7Ca0.3MnO3

We present a de magnetization study of the critical phenomena of a manganite oxide La0.7Ca0.3MnO3 single crystal. Based on the assumption of a continuous (second-order) magnetic transition for La0.7Ca0.3MnO3, we have determined the critical temperature T-C = 222 +/- 0.2 K and the critical exponents beta = 0.14 +/- 0.02 (beta: critical exponent for the temperature dependence of spontaneous magnetization just below T-c), and gamma = 0.81 +/- 0.03 (gamma: critical exponent for the inverse initial susceptibility just above T-C). The values of the critical exponents of La0.7Ca0.3MnO3 are different from those predicted based on various theoretical models, and even from those of higher T-C manganite oxides, such as La0.7Sr0.3MnO3 (T-C = 354 K). In addition, Arrot and scaling plots were found to be invalid in the immediate vicinity of Tc; this suggests that the magnetic transitional behaviors for La0.7Ca0.3MnO3 are different from those expected for a second-order transition. (C) 2001 Published by Elsevier Science Ltd.