Magnetic State of Cobalt in Layered Chalcogenide Fe4Co3Se8

Abstract

The researches of the structural and magnetic properties of the layered chalcogenide Fe₄Co₃Se₈, which has a ferrimagnetic order below T = 196 K, have been performed by means of X-ray diffraction, magnetic susceptibility measurements, and ⁵⁹Co nuclear magnetic resonance (NMR) spectroscopy. It is found that the effective magnetic moment of iron ions is μ_eff ≈ 5.90(5) μ_B. The components of the magnetic shift and electric field gradient tensors at the Co nuclei sites have been determined. The hyperfine field induced on Co nuclei from neighboring iron ions has been estimated from the temperature dependences of the shift and susceptibility in Fe₄Co₃Se₈. It was also established that cobalt ions in Fe₄Co₃Se₈, as well as in the Co₇Se₈ compound, do not have intrinsic magnetic moment, but they do have a moment induced from neighboring iron ions \(\mu _{{{\text{eff}}}}^{{{\text{Co}}}}\) ≈ 0.36(4) μ_B, which decreases at the magnetic ordering to 0.07(1)μ_B due to mutual compensation of contributions from neighboring iron ions.