Effect of compressive deformation on the martensitic transformation temperature in superconducting Nb3Sn

Superconducting Nb₃Sn, which is designed for high-field magnet fabrication, offers considerable potential for applications that range from the international thermonuclear experimental reactor to demonstration power plants (DEMO). Strain effects in Nb₃Sn superconductors are a critical issue for their engineering application in superconducting magnets, and the origin of anomalous low-temperature resistivity changes in strained Nb₃Sn remains debated. By analyzing the phonon and electronic properties of uniaxially strained Nb₃Sn during phase transitions, we develop a semianalytical trans-scale electromechanical model to characterize its low-temperature resistivity. The strain dependence of martensitic transformation temperature (Ms) is quantitatively derived from characteristic variations in normal-state resistivity under coupled thermomechanical loading. Our computation and analysis reveal the effect of compression deformation on the tetragonal-to-cubic phase transition of superconducting Nb₃Sn. Below the Ms, the variation in resistivity with temperature is predominantly governed by strain-induced changes in electronic density of states (DOS). Near the Ms point, temperature-dependent resistivity arises from the competitive interplay between strain-dependent electronic and phonon DOS variations and is accompanied with elevating Ms with increasing applied strain. Our study deepens the understanding of strain effects in superconducting Nb₃Sn, providing critical insights for establishing the relationship between phase structure and strain-affected resistivity and advancing material applications in future DEMO magnets.

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