Electron-spin resonance of a localized moment in the superconducting state:BRu2:Gd(B=La,Ce,Th)

Abstract

The electron-spin-resonance spectrum of Gd in the type-II cubic superconductors La${\mathrm{Ru}}_2$, Ce${\mathrm{Ru}}_2$, and Th${\mathrm{Ru}}_2$ has been observed in both the normal and superconducting regimes. Upon transition from the normal to the superconducting state, the spectra exhibit (a) a change in line shape ($\frac{A}{B}$ ratio), (b) an increase in thermal broadening immediately below $T_c\mathrm{}\left(H\right)\mathrm{}$, and (c) a change in $g$ value. Comparison with experiments performed by others, as well as a preliminary interpretation of the data, is presented.