Electron-Paramagnetic-Resonance Spectrum of ${\mathrm{Tc}}^{4+}$ in Single Crystals of ${\mathrm{K}}_2$Pt${\mathrm{Cl}}_6$

The electron-paramagnetic-resonance (EPR) spectrum of ${\mathrm{K}}_2$Pt${\mathrm{Cl}}_6$:${\mathrm{Tc}}^{4+}$ was measured at 0.8 and 3 cm at 4.2°K. The spectrum was fitted with a standard ${\Gamma }_8$ spin Hamiltonian with the parameters $g=1.9891\mathrm{}\pm 0.0005$, $0>u>-2.0\mathrm{}\times {10}^{-4\mathrm{}}$, $A=(1.35\mathrm{}\pm 0.01)\times {10}^{-2\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, and $U=(-1.2\mathrm{}\pm 0.1)\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. (The signs of $A$ and $U$ differ, but were not measured absolutely.) The ${\Gamma }_8$ nature was verified by the angular variation of the spectrum in the (110) plane. $\Delta m=\pm 1$ transitions were observed, and the relative intensity of these transitions with respect to the $\Delta m=0\mathrm{}$ transition is discussed.