Magnetic properties of Gd$T_2$Zn${}_{20}$ (T = Fe, Co) investigated by X-ray diffraction and spectroscopy

We investigate the magnetic and electronic properties of the Gd$T_2$Zn${}_{20}$ ($T$ = Fe and Co) compounds using X-ray resonant magnetic scattering (XRMS), X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) techniques. The XRMS measurements reveal that the GdCo${}_2$Zn${}_{20}$ compound has a commensurate antiferromagnetic spin structure with a magnetic propagation vector $\vec{\tau }$ = $(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ below the N'eel temperature ($T_N \sim$ 5.7 K). Only the Gd ions carry a magnetic moment forming an antiferromagnetic structure with magnetic representation ${\mathrm{\Gamma }}_6$. For the ferromagnetic GdFe${}_2$Zn${}_{20}$ compound, an extensive investigation was performed at low temperature and under magnetic field using XANES and XMCD techniques. A strong XMCD signal of about 12.5 $\mathrm{\%}$ and 9.7 $\mathrm{\%}$ is observed below the Curie temperature ($T_C\sim$ 85 K) at the Gd-$L_2$ and $L_3$ edges, respectively. In addition, a small magnetic signal of about 0.06 $\mathrm{\%}$ of the jump is recorded at the Zn $K$-edge suggesting that the Zn 4$p$ states are spin polarized by the Gd 5$d$ extended orbitals.