Impurity spin resonance of ${\mathrm{Fe}}^{3+}$ ions doped in the one-dimensional ferromagnet ${\mathrm{Ca}}_3{\mathrm{Co}}_2{\mathrm{O}}_6$ was investigated in a submillimeter wave region using pulsed magnetic fields at 1.7 K. As expected from the Mössbauer result, the isolated electron state of ${\mathrm{Fe}}^{3+}$ with g=2.00 was successfully observed. The D values of Fe ions are found to be 0.66 ${\mathrm{cm}}^{\mathrm{-}1}$ in a ferrimagnetic region and -0.87 ${\mathrm{cm}}^{\mathrm{-}1}$ in a ferromagnetic region which is anomalously large and would be caused by the exchange interaction between a Fe spin and surrounding Co spins.

• Received 8 May 1998

DOI:https://doi.org/10.1103/PhysRevB.58.11150