Thermal treatment and hydrostatic pressure modulation of magneto-structural transition of MnNiCoSiGe 0.5 intermetallic

This study designed a MnCoNiSiGe 0.5 intermetallic with enhanced magnetocaloric properties near room temperature and systematically investigated the effects of thermal treatment and hydrostatic pressure on magneto-structural transition and magnetic properties. Precise control over the magneto-structural transition was achieved using multi-stage annealing protocols. Increasing the annealing temperature from 873 K to 1073 K significantly reduced the transition temperature. Crucially, this heat treatment established magneto-structural coupling between the ferromagnetic orthorhombic and paramagnetic hexagonal phases. Hydrostatic pressure experiments further revealed that pressure induces the magneto-structural transition, yielding enhanced entropy changes while progressively decreasing the transition temperature. At 7.5 kbar, a barocaloric entropy change of 32.5 J•kg -1 •K -1 was achieved.Consequently, the dual regulation approach combining thermal treatment and hydrostatic pressure provides an effective strategy for tuning the working temperature range and enhancing the refrigeration capacity of such materials.