Superconducting properties of MgB${}_2$ probed by radiation-induced disordering

Abstract

The electrical resistivity $\rho$ and upper critical field $H_{c2}$ were measured in MgB${}_2$ disordered by nuclear reactor neutrons. We found that superconducting temperature $T_c$ decreases under irradiation from 40 to 5 K. Despite strong disordering (more than 10 dpa (displacements per atom)), the initial crystal structure is preserved. The residual resistivity ${\rho }_0$ increases from 0.35 to 2 m$\Omega$ cm while $-d{H}_{c2}/dT$ remains approximately unchanged ($-d{H}_{c2}/dT\approx 0.5$ T/K), and such behavior may be interpreted as decrease in the density of electronic states.

3 pages, 5 figures