Critical behavior in Ag-doped managnites La0.67Pb0.33−xAgxMnO3 (x=0.1 and 0.15)

The critical behavior of the La0.67Pb0.33−xAgxMnO3 (x=0.1 and 0.15) was investigated by measurement of the magnetization around the Curie temperature TC. Experimental results revealed that these samples exhibit a second-order magnetic phase transition. The magnetic data were analyzed in the critical region using the Kouvel-Fisher method to yield the critical exponents of 0.352≤β≤0.357 (from the temperature dependence of the spontaneous magnetization below TC), 1.272≤γ≤1.346 (from the temperature dependence of the inverse initial susceptibility above TC) and 4.563≤δ≤4.82 (from the critical magnetization isotherm M(TC, H)) with a TC of 288.37-316.39 K. The critical exponents values for La0.67Pb0.23Ag0.1MnO3 are very close to those found out by the 3D-Heisenberg model (β=0.36, γ=1.39 and δ=4.8). Moreover, the estimated critical exponents of La0.67Pb0.18Ag0.15MnO3 are consistent with the prediction of the 3D-Ising model (β=0.325, γ=1.241 and δ=4.82).