Critical behavior near the ferromagnetic-paramagnetic transformation in the austenite phase of Ni43Mn46Sn8X3 (X = In and Cr) Heusler alloys

Abstract

In this work, we present a detailed study on the magnetic property and critical behavior in the austenitic phase of Ni43Mn46Sn8X3 alloys with X=Cr and In, which were prepared by an arc-melting method in an argon ambience. The M(T) curve of the Cr sample (X=Cr) exhibits a single magnetic phase transition at the Curie temperature of the ferromagnetic (FM) austenitic phase with TAC=303K. In contrast, the In sample (X=In) exhibits multiple magnetic phase transitions, including a magnetic phase transition from a FM state to weakly magnetic state at TMC=165K of the martensitic phase, a martensitic transition from the weakly magnetic to the FM austenite phase at TM-A=259K, and a magnetic phase transition from the FM to paramagnetic (PM) at TAC=297K of the austenite phase. Based on the Landau theory and M(H) data measured at different temperatures, we pointed that the FM-PM phase transitions around TAC in both samples were the second-order phase transition. Our results suggest an existence of the long-range FM interactions in the austenite phase. A small deviation from the mean-field theory of the critical exponents has been also observed pointing out an existence of the inhomogeneous magnetism that could be associated with the presence of the anti-FM interactions in these samples. Besides, their effective exponents βeff(ε) and γeff(ε) have been also calculated.