B11NMR studies of the electronic and magnetic properties of LuRh4B4and GdRh4B4

The ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ NMR of two members of the (rare earth) ${\mathrm{Rh}}_4$ ${\mathrm{B}}_4$ series of ternary metals has been examined using wide-line techniques on powdered samples at frequencies from 6-27 MHz and temperatures of 90-300 K. In Lu${\mathrm{Rh}}_4$ ${\mathrm{B}}_4$, satellite pairs $\pm \frac{3}{2}\leftrightarrow \pm \frac{1}{2}$ transitions) flank a narrow central resonance ($\pm \frac{1}{2}\leftrightarrow \mp \frac{1}{2}$ transitions). From these quadrupolar satellites, we find $\frac{e^2\mathrm{qQ}}{h}=523\mathrm{}$ kHz and $\eta =0.37\mathrm{}$. The central transition has isotropic, $K_{\mathrm{iso}}=+0.013\%$, and anisotropic, $K_{\mathrm{anis}}=-0.124\%$, components to the Knight shift; the magnitude of $K_{\mathrm{iso}}$ as well as the residual linewidth are in agreement with our calculated values. The magnitude of $K_{\mathrm{anis}}$ is much larger than previously observed for ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$. The spectra are independent of temperature in the range 90-300 K, in contrast to the reported strong temperature dependence of the static susceptibility for this material. Magnetic interactions broaden the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ NMR for Gd${\mathrm{Rh}}_4$ ${\mathrm{B}}_4$. Paramagnetic shifts for the central component of $K_{\mathrm{iso}}=-0.263\%$ and $K_{\mathrm{anis}}=-0.56\%$ are seen; the calculated interactions between the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ nuclei and the ${\mathrm{Gd}}^{3+}$ magnetic moments are sufficient to account for both $K_{\mathrm{iso}}$ and $K_{\mathrm{anis}}$. From the observed satellite structure, we estimate $\frac{e^2\mathrm{qQ}}{h}=345\mathrm{}$ kHz, indicating that the electrostatic environment at the B sites is similar to that in Lu