Abstract:Ni-Mn-In-Co microwires with diameter of 30-100 μm are prepared by glass-coated metal filaments (Taylor–Ulitovsky) method. The effects of magnetic field on martensite transformation temperature in the as-prepared and annealed microwires are investigated using a physical property measurement system (PPMS). Magnetocaloric effect (MCE) attributed to field-induced austenite transformation in the as-prepared and annealed microwires is analyzed indirectly from the isothermal magnetization (M-B) curves. The as-prepared microwire has a 7-layer modulated martensite structure (7M) at room temperature. The changes of austenite starting temperature induced by an external magnetic field (ΔA_s/ΔB) in the as-prepared and annealed microwires are -1.6 and -4 K/T, respectively. Inverse martensite to austenite transformation exists in annealed microwires when an external magnetic field is applied at temperatures near A_s. The entropy change (ΔS) obtained in the annealed microwires is 3.0 J/(kg？K), which is much larger than that in the as-prepared microwires 0.5 J/(kg？K). The large entropy change and low price make Ni-Mn-In-Co microwires a potential working material in magnetic refrigeration.

Key words: magnetic shape memory alloys; microwires; martensitic transformation; magnetocaloric effect; magnetization curve