Charge Distribution and Hyperfine Interactions in the CuFeO 2 Multiferroic According to 63,65 Cu NMR Data

For the first time, the CuFeO2 single crystal has been studied by 63,65Cu nuclear magnetic resonance (NMR). The measurements have been carried out in the temperature range of T = 100−350 K in the magnetic field H = 117 kOe applied along different crystallographic directions. The components of the electric field gradient tensor and the hyperfine coupling constants are determined. It is shown that electrons of copper 4s and 3d orbitals are involved in the spin polarization transfer Fe → Cu. The occupancies of these orbitals are estimated.