Large magnetic circular dichroism in resonant inelastic x-ray scattering at the Mn $L$-edge of Mn-Zn ferrite

We report resonant inelastic x-ray scattering (RIXS) excited by circularly polarized x rays on Mn-Zn ferrite at the Mn $L_{2,3}$ resonances. We demonstrate that crystal-field excitations, as expected for localized systems, dominate the RIXS spectra and thus their dichroic asymmetry cannot be interpreted in terms of spin-resolved partial density of states, which has been the standard approach for RIXS dichroism. We observe large dichroic RIXS at the $L_2$ resonance which we attribute to the absence of metallic core hole screening in the insulating Mn ferrite. On the other hand, reduced $L_3$-RIXS dichroism is interpreted as an effect of longer scattering time that enables spin-lattice core hole relaxation via magnons and phonons occurring on a femtosecond time scale.

Figure 1

(Color online) Top, MCD in the Mn $2p$ x-ray absorption of ${\mathrm{Mn}}_{0.6}{\mathrm{Zn}}_{0.4}{\mathrm{Fe}}_2{\mathrm{O}}_4$ (top). ${\mathrm{I}}_{+}$ represents the XAS for the magnetization parallel to the photon spin and ${\mathrm{I}}_{-}$ represents the antiparallel. The excitation energies used for the dichroic RIXS measurements in Fig. 2 are shown by the arrows and denoted by the letters $A–G$. Bottom, calculated ${\mathrm{Mn}}^{2+}$ XAS and difference spectra in the tetrahedral $\left(T_d\right)$ symmetry.

Figure 2

(Color online) Measured Mn $L_{2,3}$ dichroic RIXS spectra denoted $A–G$ compared to crystal-field multiplet calculations in $T_d$ symmetry, plotted on an energy-loss scale. The measured spectra were excited at $640.75\mathrm{eV}$, $642.1\mathrm{eV}$, $642.4\mathrm{eV}$, $643.0\mathrm{eV}$, $644.4\mathrm{eV}$, $651.1\mathrm{eV}$, and $652.9\mathrm{eV}$ photon energies, indicated by the arrows in Fig. 1. For each photon energy, the corresponding calculated spectrum is shown below.