Critical behaviors of a second order ferromagnetic transition in martensitic state of nominal Ni49Mn39Sb12 alloy

In this study, the critical behaviors around the paramagnetic or the antiferromagnetic to ferromagnetic martensite transition in normal Ni49Mn39Sb12 alloy by bulk magnetization were investigated. The critical exponents (β, γ, and δ) have been obtained by different methods such as modified Arrott plot, Kouvel-Fisher method, and critical isotherm analysis. By these critical exponents, the data of magnetization, field and temperature around TCM collapse into two curves, obeying the single scaling equation M(H,ε)=(ε)βf±[H/ε(γ+β)]. These critical exponents are also confirmed by the Widom scaling law δ=1+γ/β. These exponents are close to those theoretically predicted by mean-field model, indicating that the magnetic interactions are long-range-like ferromagnetism around TC. In addition, the exchange distance has been obtained as J(r)=r−4.52, which also supports the long-range field-mean-like behaviors.