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

TL;DR

This study explores the magnetic and electronic properties of Gd$T_2$Zn$_{20}$ (T=Fe, Co) compounds using advanced X-ray techniques, revealing antiferromagnetic and ferromagnetic structures and spin polarization effects.

Contribution

It provides detailed magnetic structure and spin polarization insights of Gd$T_2$Zn$_{20}$ compounds using XRMS, XANES, and XMCD, which were not previously characterized.

Findings

GdCo$_2$Zn$_{20}$ exhibits antiferromagnetic order below 5.7 K.

GdFe$_2$Zn$_{20}$ shows ferromagnetic order below 85 K with significant XMCD signals.

Zn 4$p$ states are weakly spin polarized by Gd 5$d$ orbitals.

Abstract

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 $\Gamma_6$. 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 $\%$ and 9.7 $\%$ 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 $\%$ 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.