Magnetic circular dichroism of resonant x-ray emission spectroscopy for Sm L₃M_4,5 and L₂M₄ in a Sm₂₁Co₇₉ amorphous alloy

The magnetic circular dichroism (MCD) of resonant x-ray emission spectroscopy (RXES) was studied for the Sm L₃M_4,5 and L₂M₄ optical processes in a ferromagnetic Sm₂₁Co₇₉ amorphous alloy. The MCD of RXES (MCDRXES) originating from the optical process of 2p⁶3d¹⁰4fⁿ→2p⁵ 3d¹⁰4fⁿ⁺¹→2p⁶ 3d⁹4fⁿ⁺¹, which corresponds to dipolar decay after quadrupolar (E2) excitation, was obviously observed at the preedge region in addition to that of the normal dipolar (E1) excitation. Moreover, the E2 contribution of the MCD has been separated into those for E2 excitation to the Sm 4f state with majority and minority spins. A theoretical calculation based on a formula of the coherent second-order optical process was carried out for all of the experimental MCDRXES spectra. In the calculation, the multiplet coupling effect and the enhancement of the 2p-5d dipole matrix elements proposed for the MCD of x-ray absorption were taken into account. The calculated MCDRXES spectra reproduced all of the experimental results very successfully. The present result provided an appropriate interpretation of the origins of the MCD effect, which comes from the E1 and the E2 contributions at both the L₃ and the L₂ edges.