Critical Behavior Near Ferromagnetic-paramagnetic Phase Transition in Nano-polycrystalline La_(0.7)Sr_(0.3)MnO_3

Nano-polycrystalline La0.7Sr0.3MnO3 samples were fabricated by Sol-Gel method at different sintered temperatures.Field and temperature-dependent AC susceptibility has been measured in these samples.The critical peak values near their ferromagnetic-paramagnetic phase transition temperatures reveal that the curie temperature TC= 312.1K±0.2K and the critical exponents δ=3.040,γ=1.007,β=0.493 for the 973K sintered sample;TC=331.7K±0.1K,δ=2.950,γ=0.993 and β=0.508 for the 1173K sintered sample,respectively.These results consist with the mean-field theory,indicating that a long-range interaction in these materials.