Effects of heat treatments on magneto-structural phase transitions in MnNiSi-FeCoGe alloys
A first-order magneto-structural transition from a ferromagnetic orthorhombic TiNiSi-type martensite phase to a paramagnetic hexagonal Ni2In-type austenite phase was observed in (MnNiSi)0.62(FeCoGe)0.38. In this work, we demonstrate that the first-order magneto-structural transition temperature for a given composition is tunable over a wide temperature range through heat treatment and hydrostatic pressure application. The first-order transition temperature decreased by over 150 K as the annealing/quenching temperature went from 700 to 1050 °C. The largest maximum magnetic-field-induced isothermal entropy change with μ0ΔH=7 T reached −36.2 J/kg-K for the sample quenched at 700 °C, and the largest effective refrigeration capacity reached 344.5 J/kg for the sample quenched at 800 °C. Similar to the influence of annealing temperatures, the first-order martensitic transition temperatures decreased as the applied hydrostatic pressure increased until they were completely converted to second order. Our results suggest that the class of MnNiSi-based alloys is a promising platform for tailoring working temperature ranges and associated magnetocaloric effects through heat treatment or application of hydrostatic pressure.
Publication Source (Journal or Book title)
Chen, J., Poudel Chhetri, T., Us Saleheen, A., Young, D., Dubenko, I., Ali, N., & Stadler, S. (2019). Effects of heat treatments on magneto-structural phase transitions in MnNiSi-FeCoGe alloys. Intermetallics, 112 https://doi.org/10.1016/j.intermet.2019.106547