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

Department of Physics, Indian Institute of Technology Guwahati - Guwahati-781 039, Assam, India

^(a) asrini@iitg.ernet.in

Received: 11 September 2014
Accepted: 9 December 2014

Abstract

We have investigated critical behaviour and magnetocaloric effect in polycrystalline Ni₅₀Mn₃₅In₁₄Si₁ alloy near the second-order ferromagnetic phase transitions (SOPT) at austenite Curie temperature and at martensite Curie temperature by determining the critical exponents, β, γ and δ 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 at the two T_C's was estimated using the Maxwell relation as well as from the values of the critical exponents. Values of 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.