Magnetic structure in the two-dimensional van der Waals ferromagnet Fe$_3$GaTe$_2$

TL;DR

This study reports the synthesis, structural, and magnetic characterization of Fe$_3$GaTe$_2$, a two-dimensional van der Waals ferromagnet with a high Curie temperature and unique magnetic properties.

Contribution

The paper provides the first detailed structural and magnetic analysis of Fe$_3$GaTe$_2$, highlighting its high Curie temperature and the influence of lattice contraction on magnetic exchange interactions.

Findings

Fe$_3$GaTe$_2$ crystallizes in a hexagonal structure with two inequivalent Fe sites.

The magnetic easy axis is along the c axis with a Curie temperature around 355-360 K.

Lattice contraction along the c axis likely enhances Fe-Fe exchange, raising $T_C$.

Abstract

High-quality single crystals of the two-dimensional van der Waals ferromagnet Fe$_3$GaTe$_2$ (FGaT) were successfully grown using the chemical vapour transport method, which effectively reduced surface impurities compared with conventional self-flux growth. Structural and magnetic characterizations were performed using single-crystal X-ray and neutron diffraction. The results confirm that FGaT crystallizes in the hexagonal $P6_3/mmc$ structure, with Fe occupying two inequivalent sites (Fe$^{i}$ and Fe$^{ii}$), where the magnetic moment of Fe$^{i}$ [1.9(2) $\mu_B$] is larger than that of Fe$^{ii}$ [1.4(6) $\mu_B$]. The magnetic easy axis is oriented along the $c$ axis and the Curie temperature ($T_C$) is approximately 355-360 K. Compared with Fe$_3$GeTe$_2$ (FGT), FGaT exhibits a slightly expanded $a$ axis and a contracted $c$ axis, resulting in a reduction in the Fe$^{i}$-Fe$^{ii}$ interatomic distance along the $c$ axis. This pronounced contraction could strengthen the Fe$-$Fe exchange interaction, which is believed to be the key factor responsible for the significantly higher $T_C$ in FGaT relative to FGT.