Perturbed angular correlation ofCdm111in antiferromagnetic MnF2, FeF2, CoF2, and NiF2

The time-differential perturbed angular correlation (PAC) of ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}_{}^m{}_{}{}^{}$ doped into antiferromagnetic Mn${\mathrm{F}}_2$, Fe${\mathrm{F}}_2$, Co${\mathrm{F}}_2$, and Ni${\mathrm{F}}_2$ has been observed. The perturbation is caused by a combined electric-quadrupole and magnetic-dipole interaction. The PAC spectra are analyzed using autocorrelation Fourier-transformation techniques. The following quadrupole coupling parameters and internal fields have been observed (4 °K). Mn${\mathrm{F}}_2$: ${\nu }_Q=16.7+0.2\mathrm{}$ MHz, $\eta =0.05+0.02\mathrm{}$, $H_{\mathrm{int}}=34.4\mathrm{}\pm 0.8$ kOe; Fe${\mathrm{F}}_2$: ${\nu }_Q=21.6+0.3\mathrm{}$ MHz, $\eta =0.49\mathrm{}\pm 0.02$, $H_{\mathrm{int}}=40.2\mathrm{}\pm 0.8$ kOe; Co${\mathrm{F}}_2$: ${\nu }_Q=17.7\mathrm{}\pm 0.3$ MHz, $\eta =0.0\mathrm{}\pm 0.02$, $H_{\mathrm{int}}=16.4\mathrm{}\pm 0.8$ kOe; Ni${\mathrm{F}}_2$: ${\nu }_Q=16.5\mathrm{}\pm 0.3$ MHz, $\eta =0.1\mathrm{}\pm 0.08$, $H_{\mathrm{int}}=24.4\mathrm{}\pm 0.8$ kOe. The internal fields are perpendicular to the $z$ axis, $z_{\mathrm{FG}}$, of the field-gradient tensor for Mn${\mathrm{F}}_2$, Fe${\mathrm{F}}_2$, and Co${\mathrm{F}}_2$, parallel to $y_{\mathrm{FG}}$ in Mn${\mathrm{F}}_2$, and pointing along $x_{\mathrm{FG}}$ in Fe${\mathrm{F}}_2$. In Ni${\mathrm{F}}_2$ the internal field is found in the $z_{\mathrm{FG}}$, $x_{\mathrm{FG}}$ plane tilted by approximately 48 ° ± 5 ° against the $z_{\mathrm{FG}}$ axis. The hyperfine fields are caused by unpaired spin density transferred into Cd $s$ orbitals from two nearest and eight next-nearest magnetic ions belonging to two different sublattices. The internal fields are compared with those found in the corresponding perovskites KNi${\mathrm{F}}_3$, KCo${\mathrm{F}}_3$, KFe${\mathrm{F}}_3$, and RbMn${\mathrm{F}}_3$.