Temperature dependence of magnetic susceptibility in the vicinity of martensitictransformation in ferromagnetic shape memory alloys

Abstract

Temperature dependences of low-field quasistatic magnetic susceptibility in the vicinity ofmartensitic transitions in an NiFeGa alloy are studied both by experiment and analytically.Pronounced reversible jumps of the magnetic susceptibility were observed near themartensitic transition temperature. A general description of the temperature dependencesof the susceptibility in ferromagnetic austenite and martensite phases and the susceptibilityjump at the transition is suggested. As a result, the main factors governing thetemperature dependences of the magnetic susceptibility in the magnetic shape memoryalloys are revealed. The magnetic susceptibility jump value is found to be related tochanges of: (i) magnetic anisotropy; (ii) magnetic domain wall geometrical constraints (thosedetermined by the alignment and size of twin variants) and (iii) mean magnetic domainspacing.