Electron Spin Resonance ofMo5+in CaWO4

Electron-spin-resonance measurements of ${\mathrm{Mo}}^{5+}$ in CaW${\mathrm{O}}_4$ have been carried out at about 4.2°K and 9.2 Gc/sec. The $g$ values parallel and perpendicular to the $c$ axis are 1.987 and 1.887, respectively. The hyperfine-splitting constants for the two isotopes (${\mathrm{Mo}}^{95}$ and ${\mathrm{Mo}}^{97}$) of molybdenum in units of ${10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$ are ${A_{\mathrm{II}}}^{\mathrm{}\left(95\right)\mathrm{}}=8.39\mathrm{}$, ${A_{\perp }}^{\mathrm{}\left(95\right)\mathrm{}}=41.18\mathrm{}$, ${A_{\mathrm{II}}}^{\mathrm{}\left(97\right)\mathrm{}}=8.64\mathrm{}$ and ${A_{\mathrm{II}}}^{\mathrm{}\left(97\right)\mathrm{}}=42.52\mathrm{}$.