High‐Entropy Nanostructured Hydride Network Enables Giant Magnetocaloric Effects and Exceptional Plasticity

ABSTRACT Achieving a giant magnetocaloric effect (MCE) with negligible hysteresis and excellent strength–plasticity balance poses a significant challenge due to inherently conflicting trade‐offs. Here, we develop a high‐entropy nanostructured glass‐hydride (HENGH) featuring a percolating nano‐hydride network in a glass phase, which achieves an unprecedented combination of giant MCE, near‐zero hysteresis, and exceptional mechanical properties. HENGH exhibits a maximum magnetic entropy change of 11.3 J kg −1 K −1 for a field change of 2 T, 200% higher than the hydrogen‐free counterpart. Simultaneously, it achieves a yield strength of 2.2 GPa with over 50% plastic strain, beating the strength–plasticity trade‐off. It's revealed that the nanostructured glass‐hydride network with competing magnetic orders shifts transitions from 3D Ising to tricritical mean‐field behavior, combining giant MCE from first‐order transition with minimal hysteresis from second‐order one. Moreover, unlike conventional hydrogen embrittlement, hydrogenation here enables a brittle‐to‐ductile transition via collaborative deformation of nanostructured hydride and glass phases. Specifically, nano‐hydride deformation triggers nucleation of the shear transformation zone in the glass phase, while their interaction with shear bands induces their multiplication and hydride's rotation or division. The HENGH system, an emerging subclass of high‐entropy materials, achieves an exceptional MCE–strength–plasticity synergy, providing a new platform for multifunctional material design.