Relation between Electron Spin Resonance and Nuclear Magnetic Resonance in Transition Metal Intermetallic Compounds

Abstract

A single system of intermetallic compounds, ${\mathrm{La}}_{1-x}{\mathrm{Th}}_x{\mathrm{Ru}}_2$, has been found in which both the nuclear magnetic resonance of ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$ and the electron spin resonance of added Gd impurities can be observed. Both the NMR Knight shift and the ESR $g$ shift were measured and found to vary with composition $x$. Linear relationships between $g$ and $K$ and between $K$ and $x$ were found as composition and temperature were varied, from which the effective exchange between spins of the Gd $4f$ electrons and the $d$ electrons of the formula unit was found to be -0.05 eV. The variations in $g$ and $K$ also allowed the magnitudes of the several sources of magnetic susceptibilities of the compounds to be evaluated. ${{\chi }_{6s}}^{\mathrm{spin}}\le 0.07\times {10}^{-4\mathrm{}}$ emu/mole, and ${{\chi }_{5d}}^{\mathrm{spin}}$ varies from 2.0×${10}^{-4\mathrm{}}$ at 1.4°K to 1.0×${1.0}^{-4\mathrm{}}$ at 300°K in La${\mathrm{Ru}}_2$, while the field-induced temperature-independent orbital paramagnetism of the $d$ bands is less than 0.7×${10}^{-4\mathrm{}}$ emu/mole for the La site in La${\mathrm{Ru}}_2$ and between 1.8×${10}^{-4\mathrm{}}$ and 2.4×${10}^{-4\mathrm{}}$ emu/mole for the Ru site in La${\mathrm{Ru}}_2$. A reversal in sign of the temperature dependence of the NMR Knight shift as composition was varied is interpreted in terms of changes in the density of electronic states at the Fermi surface as Th is alloyed in place of La.