XMCD at the L II , III edges of Er in ErMn 2 , ErFe 2 , ErCo 2 , ErNi 2 , and ErAl 2 Laves phases and in Er 2 ( SO 4 ) 3 , 8 H 2 0

X-ray magnetic circular dichroism (XMCD) measurements have been performed at the ${\mathit{L}}_{\text{II},\text{III}}$ edges of Er in the intermetallic compounds ${\text{ErMn}}_{2}$, ${\text{ErFe}}_{2}$, ${\text{ErCo}}_{2}$, ${\text{ErNi}}_{2}$, and ${\text{ErAl}}_{2}$, as well as in the ionic compound ${\text{Er}}_{2}{({\text{SO}}_{4})}_{3},8{\mathrm{H}}_{2}0$, in order to study the evolution of the XMCD spectra as a function of the $5d$ states filling and∕or their hybridization with magnetic or nonmagnetic electronic states. Almost all the spectra present the same general features, confirming that the $4f\text{\ensuremath{-}}5d$ intra-atomic coupling is a key point to explain XMCD spectra. Thus, we analyze the models based on this interaction, proposed to account for the unexpected sign of $\mathit{E}1\text{\ensuremath{-}}\text{XMCD}$ measurements, as well as the nonstatistical branching ratio between XMCD at the ${\mathit{L}}_{\text{II}}$ and ${\mathit{L}}_{\text{III}}$ edges. We underline the impossibilities of reproducing our measurements using these models. Moreover, we point out the special role played by Fe which leads, at the ${\mathit{L}}_{\text{II}}$ edge of Er, to a significant modification of the shape of XMCD spectrum and an unexpected temperature dependence. The XMCD revealed an unexpected behavior of the $5d$ magnetic polarization in these compounds which is not visible in macroscopic measurements. This also demonstrates the non-negligible role played by the $5d\text{\ensuremath{-}}3d$ hybridization.