Time and magnetic field dependent magnetic order in Ca3Co2O6 revealed by resonant x-ray scattering

The observation of time dependent magnetic order in the spin-chain compound Ca3Co2O6, a promising candidate for showing out-of-equilibrium magnetization behavior, has received tremendous attention for over a decade. The present study uses resonant magnetic scattering close to the cobalt K-absorption edge to probe directly the time, temperature, and magnetic field dependence of the magnetic order in a Ca3Co2O6 single crystal. Energy dependences of the magnetic signal and their simulation suggest that the resonant x-ray scattering (RXS) signal at the pre-edge contains contributions only from quadrupole (E2E2) and dipolar-quadrupolar (E1E2) transition processes. Interestingly, the flat intensity variation as a function of azimuthal angle over a wide angular range cannot be explained by considering the ordering of magnetic dipole moments alone. The observed magnetic order below the Neel temperature TN in the present RXS study differs significantly from the reported neutron diffraction results, indicating possible contributions from high-order moments in addition to the magnetic dipole moment.