Near-room temperature barocaloric effect governed by the magneto-structural coupling of isostructural MnNiGe-FeCoSn alloys

New solid-state refrigeration technologies based on caloric effects offer an energy-efficient and environmentally friendly alternative to conventional gas-compression refrigeration. In this paper, the geometric compatibility of the magnetic structural phase transition near room temperature is tailored via precise isostructural alloying. A (MnNiGe) 0.97 (FeCoSn) 0.03 alloy exhibiting a small thermal hysteresis (Δ T hys ) near room temperature was synthesized, which leads to an enhanced reversible barocaloric effect. A small Δ T hys of 4.7 K and a larger shift of the martensitic transformation temperature by the applied pressure ( dT/dP = −6.5 K∙kbar -1 ) are obtained. At an ultra-low pressure of 0.6 kbar, the alloy achieves a reversible isothermal entropy change (Δ S rev ) of 5.7 J·kg −1 ·K −1 and a reversible adiabatic temperature change (Δ T rev ) of 1.1 K, respectively, successfully shows a low-pressure driven partial reversible barocaloric effect. This originates primarily from the combination of a small Δ T hys (4.7 K), a large cell volume expansion (Δ V/V = 2.7%) and a structural transformation entropy change (Δ S tr = 57.7 J·kg −1 ·K −1 ).