Critical exponents of the second-order manganite Nd_(0.5)Sr_(0.25)Ca_(0.25)MnO_3 determined from magnetic entropy change measurements

摘要

The critical exponents of second-order phase transition were deduced from magnetic entropy change. Using the magnetic field dependence of entropy change and the Widom scaling relation, some relevant critical exponents can be calculated directly from them. Based on critical exponents, a corresponding Arrott plot can be established as an initial model. Through a limited nonlinear fitting, we can obtain the final critical exponents. This method eliminates the drawbacks of the routine method which relies on the subjective selection of an initial model and involves the multi-step nonlinear fitting process. It was applied to the manganite Nd_(0:5)Sr_(0:25)Ca_(0:25)MnO_3 to verify its utility and feasibility. The spontaneous magnetization obtained using the final critical exponents is consistent with that deduced from the isothermal magnetization measurements, indicating that the utilization of the magnetic field dependence of magnetic entropy change to determine critical exponents is a valid method.