Antiferromagnetic Resonance andMn55Nuclear Magnetic Resonance in Cobalt-Doped RbMnF3

Single crystals of Co-doped RbMn${\mathrm{F}}_3$ have been grown by the Czochralski method, with doping concentrations ranging from zero to about 1500 ppm. It is found from antiferromagnetic-resonance (AFMR) measurements that the crystalline cubic anisotropy constant $K_1$ varies in a fairly linear manner with Co concentration. There appears to be little or no increase in $K_2$. The constant $K_1$ becomes zero at about 340-ppm Co concentration. AFMR and ${\mathrm{Mn}}^{55}$ nuclear resonance have been investigated experimentally over a wide frequency range. The data agree well with the computed mode spectra. The results imply that the sublattice magnetizations and the exchange and effective nuclear hyperfine fields are essentially unaffected by the presence of the Co. Some additional modes have been observed which are not predicted by the theory.