The Forced Magnetostrictions and Magnetic Properties of Ni(2)MnX (X = In, Sn) Ferromagnetic Heusler Alloys

Experimental studies into the forced magnetostriction, magnetization, and temperature dependence of permeability in Ni(2)MnIn and Ni(2)MnSn ferromagnetic Heusler alloys were performed according to the spin fluctuation theory of itinerant ferromagnetism proposed by Takahashi. We investigated the magnetic field (H) dependence of magnetization (M) at the Curie temperature T(C), and at T = 4.2 K, which concerns the ground state of the ferromagnetic state. The M-H result at T(C) was analyzed by means of the H versus M(5) dependence. At 4.2 K, it was investigated by means of an Arrott plot (H/M vs. M(2)) according to Takahashi’s theory. As for Ni(2)MnIn and Ni(2)MnSn, the spin fluctuation parameters in k-space (momentum space, T(A)) and that in energy space (frequency space, T(0)) obtained at T(C) and 4.2 K were almost the same. The average values obtained at T(C) and 4.2 K were T(A) = 342 K, T(0) = 276 K for Ni(2)MnIn and T(A) = 447 K, T(0) = 279 K for Ni(2)MnSn, respectively. The forced magnetostriction at T(C) was also investigated. The forced linear magnetostriction (ΔL/L) and the forced volume magnetostriction (ΔV/V) were proportional to M(4), which followed Takahashi’s theory. We compared the forced volume magnetostriction ΔV/V and mechanical parameter, bulk modulus K. ΔV/V is inversely proportional to K. We also discuss the spin polarization of Ni(2)MnIn and other magnetic Heusler alloys. The p(C)/p(S) of Ni(2)MnIn was 0.860. This is comparable with that of Co(2)MnGa, which is a famous half-metallic alloy.