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

We present a dc 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 TC=222±0.2 K and the critical exponents β=0.14±0.02 (β: critical exponent for the temperature dependence of spontaneous magnetization just below TC), and γ=0.81±0.03 (γ: critical exponent for the inverse initial susceptibility just above TC). 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 TC manganite oxides, such as La0.7Sr0.3MnO3 (TC=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.