The alloy ${\text{Ni}}_{45}{\text{Co}}_5{\text{Mn}}_{40}{\text{Sn}}_{10}$ is shown to be singular relative to nearby alloys in three following ways: (1) The austenite has remarkably high magnetization $\left(1170\text{emu}/{\text{cm}}^3\right)$ and low magnetic anisotropy. (2) The thermal hysteresis is near minimum. (3) The transformation temperature $\sim 135°\text{C}$ is unusually high. Because the unusually large magnetization and low hysteresis is seen at relatively small applied fields, applications such as magnetic shape memory, energy conversion, and solid state refrigeration may become practical.

Structural phase transitions serve as the basis for many functional applications including shape memory alloys (SMAs), switches based on metal-insulator transitions (MITs), etc. In such materials, lattice incompatibility between transformed and parent phases often results in a thermal hysteresis, which is intimately tied to degradation of reversibility of the transformation. The non-linear theory of martensite suggests that the hysteresis of a martensitic phase transformation is solely determined by the lattice constants, and the conditions proposed for geometrical compatibility have been successfully applied to minimizing the hysteresis in SMAs. Here, we apply the non-linear theory to a correlated oxide system (V_1−xW_xO₂), and show that the hysteresis of the MIT in the system can be directly tuned by adjusting the lattice constants of the phases. The results underscore the profound influence structural compatibility has on intrinsic electronic properties, and indicate that the theory provides a universal guidance for optimizing phase transforming materials.