Effect of neutron irradiation on single-crystalV3Si: Sound velocity, magnetic susceptibility, and upper critical field

We have measured the sound velocity, magnetic susceptibility, and upper superconducting critical field $H_{c2\mathrm{}}$ of a single crystal of V ${}_3{}^{}{}_{}{}^{}\mathrm{Si}$ as a function of neutron irradiation up to a fluence of 22.2 × ${10}^{18}$ n/${\mathrm{cm}}^2$. Very small doses affect the structural transormation, while leaving the superconducting transition temperature $T_c$, the soft acoustic shear mode, the susceptibility $\chi$, and $H_{c2\mathrm{}}$ essentially unaltered. At higher defect concentrations, the strong anomalous temperature dependences of $\chi$ and the elastic modulus $c_s$ are considerably reduced, although significant anomalies remain for the highest fluence (which lowers $T_c$ from 17.2 to 7.4 K). Within models which assume unusual fine structure in the electronic density of states near the Fermi level, our results imply that defects produce broadening and smearing of the density-of-states function.