Influence of Ga doping on the critical behavior of La0.7(Ba,Sr)0.3Mn1-xGaxO3

Abstract

The critical properties of the manganese perovskite La0.7(Ba, Sr)0.3Mn1-xGaxO3 (x = 0.0, 0.1 and 0.2) around the paramagnetic–ferromagnetic phase transition were investigated using modified Arrott plots and Kouvel–Fisher method based on the data of static magnetic measurements recorded around the Curie temperature TC. For all compounds, the obtained values of critical exponents were found to satisfy the scaling theory. Moreover, the critical exponents are confirmed by the field dependence of the magnetic entropy change relation ΔSM=aHn The critical exponents values of our samples are very close to those found by the mean-field model (β = 0.5, γ = 1 and δ = 3). These results indicate long-range ferromagnetic coupling in La0.7(Ba, Sr)0.3Mn1-xGaxO3 (x = 0.0, 0.1 and 0.2), which cannot be explained by the nearest–neighbor interaction proposed for the double-exchange mechanism.