Electron Spin Resonance and Superconductivity inGdxLa1−xAl2Intermetallic Compounds

Abstract

Electron-spin-resonance measurements of Gd in La${\mathrm{Al}}_2$ exhibit appreciable change of the $g$ value and linewidth upon alloying with other nonmagnetic impurities. This indicates the existence of a "bottleneck" effect—the relaxation rate for the conduction electrons to the Gd ions ${\delta }_{\mathrm{ei}}$ exceeds that to the lattice ${\delta }_{\mathrm{eL}}$. We are able to shift the $g$ value from $g=1.988\mathrm{}\pm 0.003$ to $g=2.11\mathrm{}\pm 0.01$, opening the bottleneck completely. The intermetallic compounds $\mathrm{Gd}{\mathrm{La}}_{1-x}{\mathrm{Al}}_2$ are Abrikosov-Gorkov superconductors in the dilute limit. Measurements of the transition temperature and the upper critical field depend upon ${\delta }_{\mathrm{ei}}$ directly and ${\delta }_{\mathrm{eL}}$ indirectly. We are thus able to obtain parameters which determine superconducting critical-field and temperature behavior from magnetic resonance experiments.