Paramagnetic Resonance Spectra ofCr3+in ZnWO4

Abstract

Paramagnetic resonance measurements have been carried out at millimeter and centimeter wavelengths on ${\mathrm{Cr}}^{3+}$ ions diluted in single crystals of ZnW${\mathrm{O}}_4$ grown from the melt. The spectrum is described by the spin Hamiltonian $H=D[{S_z}^2-\frac{1}{3}S(S+1\mathrm{}\left)\right]+E({S_x}^2-{S_y}^2)+\beta (g_x{H}_x{S}_x+g_y{H}_y{S}_y+g_z{H}_z{S}_z)+A\mathrm{I}·\mathrm{S},$ with $S=\frac{3}{2}$; $D=+25.47\mathrm{}\pm 0.01$ kMc/sec; $E=-2.42\mathrm{}\pm 0.03$ kMc/sec; $g_x=1.958\mathrm{}\pm 0.002$; $g_y=1.962\mathrm{}\pm 0.002$, and $g_z=1.968\mathrm{}\pm 0.002$ at 293°K. The spin-orbit coupling constant found from these parameters is positive as expected. The magnetic hyperfine splitting factor $\mathrm{}\left|A\right|\mathrm{}$ for ${\mathrm{Cr}}^{53}$ ($I=\frac{3}{2}$) was found to be 0.052±0.002 kMc/sec at 4.2°K and isotropic within the limits of error. The magnetic $y$ axis is parallel to the monoclinic $b$ axis and the magnetic $z$ axis is rotated away from the crystal $+a$ axis toward the $+c$ axis by 4.2±0.5 deg.