Nuclear Magnetic Resonance of Cd in Cd${\mathrm{Cr}}_2$${\mathrm{Se}}_4$ and Cd${\mathrm{Cr}}_2$${\mathrm{S}}_4$, and Transferred Spin Polarization in Chromium Chalcogenide Spinels

Purely isotropic hyperfine fields have been observed for ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$ and ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ by zero-field NMR in both ferro-magnetic Cd${\mathrm{Cr}}_2$ ${\mathrm{Se}}_4$ and Cd${\mathrm{Cr}}_2$ ${\mathrm{S}}_4$. The values at 4.2 K are + 136.2±0.2 and (+) 167.0±0.2 kOe, respectively. Combined with earlier results for ${}_{}{}^{53}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{77}{}_{}{}^{}\mathrm{Se}$ in Cd${\mathrm{Cr}}_2$ ${\mathrm{Se}}_4$, this work allows estimates to be made of the amount of unpaired spin covalently transferred to the nonmagnetic ions. Transfers between ligands and the $4s$ level of ${\mathrm{Cr}}^{3+}$ are particularly important. Some consequences for the magnetic properties of the system are discussed.