ESR ofGd3+in the Kondo-lattice compoundYbAgCu4and its reference compoundsRAgCu4(R=Y,Lu)

Abstract

Low-temperature $(T<30\mathrm{K})$ electron-spin-resonance (ESR) experiments of ${\mathrm{Gd}}^{3+}$ diluted in the Kondo-lattice compound ${\mathrm{YbAgCu}}_{4}$ and its reference compounds ${\mathrm{YAgCu}}_{4}$ and ${\mathrm{LuAgCu}}_{4}$ are interpreted in terms of an enhanced density of states at the Fermi level for the Yb-based compound. The results of susceptibility and ESR (Korringa rate and $g$-shift) measurements show negligible electron-electron exchange enhancement for all the studied compounds. The exchange interaction between the ${\mathrm{Gd}}^{3+}$ local moment and the conduction electrons (c-e) is c-e wave vector dependent in all three compounds.