Electronic Structures of Ferromagnetic CeAgSb$_2$:Soft X-ray Absorption, Magnetic Circular Dichroism and Angle-Resolved Photoemission Spectroscopies

摘要

We report a combined study for the electronic structures of ferromagneticCeAgSb$_2$ using soft X-ray absorption (XAS), magnetic circular dichroism(XMCD), and angle-resolved photoemission (ARPES) spectroscopies. The Ce $M_{4,5}$ XAS spectra show very small satellite structures, reflecting a stronglylocalized character of the Ce $4f$ electrons. The linear dichroism effects inthe Ce $M_{4, 5}$ XAS spectra demonstrate the ground state Ce $4f$ symmetry of$\Gamma{_6}$, the spatial distribution of which is directed along the $c$-axis.The XMCD results give support to the picture of local-moment magnetism inCeAgSb$_2$. Moreover it is also found that the theoretical band dispersions forLaAgSb$_2$ provides better description of the ARPES band structures than thosefor CeAgSb$_2$. Nevertheless, ARPES spectra at the Ce $3d$-$4f$ resonance showthe momentum dependence for the intensity ratio between Ce $4f^{1}_{5/2}$ and$4f^{1}_{7/2}$ peaks in a part of the Brillouin zone, suggesting thenon-negligible momentum dependent hybridization effect between the Ce $4f$ andthe conduction electrons. This is associated with the moderate mass enhancementin CeAgSb$_2$.