摘要: The rising global temperatures alongside increasing energy demands highlight the imperative for sustainable and energy-efficient refrigeration technologies. Magnetic refrigeration, which is based on the magnetocaloric effect (MCE), presents a compelling solid-state alternative to traditional vapor-compression systems. However, many high-performance magnetocaloric materials rely on critical elements such as rare earths, cobalt, or germanium. Despite extensive compositional flexibility, high-entropy alloys (HEAs) have predominantly been investigated in equiatomic compositions incorporating significant quantities of highly critical elements to achieve large MCE or mixing rare earth elements in majority proportions that only yield moderate MCE values, thereby failing to address issues of material criticality. In this study, we present a criticality-aware design strategy for the MnNiSi-HEA system, exemplifying a prototype of the latest third-generation HEAs. Various substitutional approaches were evaluated to achieve the coupling between magnetic and structural transitions. The most effective pathway, identified through the co-substitution of Fe and Cu, reduces the structural transition temperature by over 900 K relative to MnNiSi while preserving the ferromagnetic characteristics of the low-temperature phase, successfully inducing a first-order magnetostructural transformation near room temperature. The resulting alloys, Mn_0.5Fe_0.5Ni_1-xCu_xSi, exhibit coupled transitions spanning more than 100 K and demonstrate the highest MCE reported to date among HEAs free of cobalt, germanium, and rare earth elements, outperforming previous records by 360 %. Complementary DFT calculations confirm the stability of the orthorhombic and hexagonal phases. Predictions of lattice entropy change closely match calorimetric measurements. This research establishes a new benchmark for low-criticality magnetocaloric HEAs, underscoring that optimal functional performance and sustainable material development can be achieved concomitantly. The proposed design methodology offers a valuable framework for advancing resourceresilient solid-state cooling materials and underscores the potential of HEAs as a platform for sustainable functional materials.