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

Abstract

The observation of time dependent magnetic order in the spin-chain compound ${\mathrm{Ca}}_{3}{\mathrm{Co}}_{2}{\mathrm{O}}_{6}$, 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 ${\mathrm{Ca}}_{3}{\mathrm{Co}}_{2}{\mathrm{O}}_{6}$ 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 N\'eel temperature ${T}_{N}$ 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.