First-order-like magnetic transition in manganite oxide La 0.7Ca 0.3MnO 3

Abstract

We present a dc magnetization study of the critical phenomena of a manganite oxide La 0.7Ca 0.3MnO 3 single crystal. Based on the assumption of a continuous (second-order) magnetic transition for La 0.7Ca 0.3MnO 3, we have determined the critical temperature T C=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 T C), and γ=0.81±0.03 ( γ: critical exponent for the inverse initial susceptibility just above T C). The values of the critical exponents of La 0.7Ca 0.3MnO 3 are different from those predicted based on various theoretical models, and even from those of higher T C manganite oxides, such as La 0.7Sr 0.3MnO 3 ( T C=354 K). In addition, Arrot and scaling plots were found to be invalid in the immediate vicinity of T C; this suggests that the magnetic transitional behaviors for La 0.7Ca 0.3MnO 3 are different from those expected for a second-order transition.