The Forced Magnetostrictions and Magnetic Properties of NiMnX (X = In, Sn) Ferromagnetic Heusler Alloys.

Experimental studies into the forced magnetostriction, magnetization, and temperature dependence of permeability in NiMnIn and NiMnSn ferromagnetic Heusler alloys were performed according to the spin fluctuation theory of itinerant ferromagnetism proposed by Takahashi. We investigated the magnetic field () dependence of magnetization () at the Curie temperature , and at = 4.2 K, which concerns the ground state of the ferromagnetic state. The - result at was analyzed by means of the versus dependence. At 4.2 K, it was investigated by means of an Arrott plot (/ vs. ) according to Takahashi's theory. As for NiMnIn and NiMnSn, the spin fluctuation parameters in -space (momentum space, ) and that in energy space (frequency space, ) obtained at and 4.2 K were almost the same. The average values obtained at and 4.2 K were = 342 K, = 276 K for NiMnIn and = 447 K, = 279 K for NiMnSn, respectively. The forced magnetostriction at was also investigated. The forced linear magnetostriction (Δ/) and the forced volume magnetostriction (Δ/) were proportional to , which followed Takahashi's theory. We compared the forced volume magnetostriction Δ/ and mechanical parameter, bulk modulus . Δ/ is inversely proportional to . We also discuss the spin polarization of NiMnIn and other magnetic Heusler alloys. The / of NiMnIn was 0.860. This is comparable with that of CoMnGa, which is a famous half-metallic alloy.