THE EFFECT OF CO-DOPING ON SPIN CLUSTER RESONANCE IN THE ONE-DIMENSIONAL ISING FERROMAGNET FETAC

Electron paramagnetic resonance measurements at 36 GHz and in the rang e 12-18 GHz were made on a single crystal of the 1D Ising ferromagnet [(CH3)3 NH] FeCl3.2H2O, known as FeTAC, containing a nominal 10% of th e isomorphous compound CoTAC. While the 4.2 K spectra obtained with th e external field parallel to the chain axis were similar to the spin c luster resonance spectra previously identified in pure FeTAC, differen ces in the low-field satellite structure were observed, which are tent atively attributed to differences in the dipolar interaction and to sh orter ferrous chains. An appreciable decrease in the strength of the d emagnetizing field is associated with the tendency of the Co2+ moments to align perpendicularly to the chain axis.