Electron spin resonance of Nd3+ and Gd3+ in d-band intermetallic compounds

We report on the ESR of the rare-earth ions Nd3+, Gd3+, Er3+, and Yb3+ on powdered samples of various intermetallic compounds of AB2 cubic structure where B is a transition-metal ion belonging to the group VIII of the Periodic Table, and A is a nonmagnetic ion (La, Ce, Y). The resonance of the Nd3+ in these compounds originates within a Γ6 crystal-field ground level and exhibits resolved hyperfine satellites for the Nd143 and Nd145 isotopes. The Gd3+ spectra show a single isotropic line. Using our data for Gd3+ and Nd3+ together with results previously published for the AB2 cubic compounds, we were able to show a correlation between the observed g shifts and the position of the B ion in the Periodic Table. This variation is explained qualitatively using a simple multiband model, as well as band-structure arguments. The hyperfine constants for the Nd143 and Nd145 isotopes were found smaller in magnitude with respect to the values in insulators; this effect is attributed to s-electron self-polarization due to the Nd localized-moment-s-electron exchange coupling. The ESR linewidths of LaIr2: Nd and LaRh2: Nd exhibit an exponential thermal dependence at high temperatures which is attributed to the presence of a Γ8 excited level at Δ=90±20 K.