Composition‐Engineered Hexagonal MM′X Alloys With Giant Magnetocaloric and Barocaloric Effects Over a Wide Temperature Range

ABSTRACT Functional multicaloric materials exploit the strong coupling between multiple thermodynamic fields and offer a promising route toward compact and environmentally friendly solid‐state refrigeration. Here, composition engineering is employed to develop a series of hexagonal MM′X‐type MnFeNiCoGeSi alloys exhibiting giant magnetocaloric and barocaloric effects over a wide temperature range. A first‐order magnetostructural transition produces concurrent discontinuities in magnetization and lattice volume, yielding both notable magnetocaloric and barocaloric response across 260–340 K with entropy changes above 47.3 J/kgK (magnetic field variation of 5 T) and 36.3 J/kgK (low pressure of 60 MPa), respectively, both surpassing most representative multicaloric materials. The large disparity between the sensitivity of the transition temperatures to hydrostatic pressure ( T C /d p = –49.4 K/GPa) and magnetic field (d T C /d μ 0 H = 1.2 K/T) provides exceptional tunability of the magnetostructural transition under coupled external stimuli. Consequently, under 1.16 GPa and a magnetic field change of 2 T, the refrigerant capacity increases from 65.14 to 73.53 J/kg relative to ambient pressure, accompanied by a remarkable transition‐temperature shift of approximately 60 K. These findings establish multicomponent MnFeNiCoGeSi alloys as a promising platform for designing multicaloric refrigeration technologies.