Critical behavior and magnetic entropy change at magnetic phase transitions in Ni50Mn35In14Si1 ferromagnetic shape memory alloy

We have investigated critical behaviour and magnetocaloric effect in polycrystalline Ni50Mn35In14Si1 alloy near the second-order ferromagnetic phase transitions (SOPT) at austenite Curie temperature (T-C,T- (A)) and at martensite Curie temperature (T-C,T- M) by determining the critical exponents, beta, gamma and delta corresponding to the temperature dependence of spontaneous magnetization, initial susceptibility and isothermal magnetization, respectively. The field dependence of the maximum value of the magnetic entropy change (Delta S-M) at the two T-C's was estimated using the Maxwell relation as well as from the values of the critical exponents. Values of Delta S-M obtained by these two methods at both the SOPT are in remarkable agreement with each other. The critical exponents have been determined by analysing isothermal magnetization data using two different methods, viz., the modified Arrott plot method and the Widom scaling relation. The scaling plots depicted on linear as well as logarithmic scales confirm the reliability of the values of critical exponents obtained. The values of the critical exponents of polycrystalline Ni50Mn35In14Si1 alloy at both the T-C's are close to those predicted by mean-field theory confirming the presence of long-range magnetic ordering in the investigated alloy. Copyright (C) EPLA, 2014