Magnetic Order in TbCo2Zn20 and TbFe2Zn20

TL;DR

This study investigates the magnetic behaviors of TbCo2Zn20 and TbFe2Zn20 using neutron diffraction, revealing antiferromagnetic order in the former and highly sample-sensitive ferromagnetic order in the latter, influenced by subtle structural differences.

Contribution

The paper provides detailed neutron diffraction analysis showing the impact of minor structural variations on magnetic order in TbFe2Zn20, highlighting its extreme sensitivity to disorder.

Findings

TbCo2Zn20 exhibits antiferromagnetic order below 2.5 K.

TbFe2Zn20 shows ferromagnetic transition around 66 K.

Small structural differences influence magnetic properties significantly.

Abstract

We report neutron diffraction studies of TbCo$_2$Zn$_{20}$ and TbFe$_2$Zn$_{20}$, two isostructural compounds which exhibit dramatically different magnetic behavior. In the case of TbCo$_2$Zn$_{20}$, magnetic Bragg peaks corresponding to antiferromagnetic order are observed below $T_N$ $\approx$ 2.5 K with a propagation vector of (0.5 0.5 0.5). On the other hand, TbFe$_2$Zn$_{20}$ undergoes a ferromagnetic transition at temperatures as high as 66 K which shows a high sensitivity to sample-to-sample variations. Two samples of TbFe$_2$Zn$_{20}$ with the same nominal compositions but with substantially different magnetic ordering temperatures ($T_c$ $\approx$ 51 and 66 K) were measured by single crystal neutron diffraction. Structural refinements of the neutron diffraction data find no direct signature of atomic site disorder between the two TbFe$_2$Zn$_{20}$ samples except for subtle differences in the anisotropic thermal parameters. The differences in the anisotropic thermal parameters between the two samples is likely due to very small amounts of disorder. This provides further evidence for the extreme sensitivity of the magnetic properties of TbFe$_2$Zn$_{20}$ to small sample variations, even small amounts of disorder.