Tuning the Room Temperature Ferromagnetism in Fe5GeTe2 by Arsenic Substitution

TL;DR

This study investigates how arsenic substitution affects the magnetic properties of Fe$_{5-x}$GeTe$_2$, revealing enhancements and reductions in ferromagnetism depending on arsenic content, and explores the magnetic behavior of Fe$_{4.8}$AsTe$_2$ crystals.

Contribution

It demonstrates the impact of arsenic substitution on tuning the magnetic order in Fe$_{5-x}$GeTe$_2$ and reports the synthesis and magnetic characterization of Fe$_{4.8}$AsTe$_2$.

Findings

Small arsenic additions enhance ferromagnetic order.

Larger arsenic concentrations decrease Curie temperature and magnetization.

Fe$_{4.8}$AsTe$_2$ exhibits antiferromagnetic behavior with a Nel temperature of 42K.

Abstract

In order to tune the magnetic properties of the cleavable high-Curie temperature ferromagnet Fe$_{5-x}$GeTe$_2$, the effect of increasing the electron count through arsenic substitution has been investigated. Small additions of arsenic (2.5 and 5%) seemingly enhance ferromagnetic order in polycrystalline samples by quenching fluctuations on one of the three magnetic sublattices, whereas larger As concentrations decrease the ferromagnetic Curie temperature ($T_{\rm C}$) and saturation magnetization. This work also describes the growth and characterization of Fe$_{4.8}$AsTe$_2$ single crystals that are structurally analogous to Fe$_{5-x}$GeTe$_2$ but with some phase stability complications. Magnetization measurements reveal dominant antiferromagnetic behavior in Fe$_{4.8}$AsTe$_2$ with a N\'{e}el temperature of $T_{\rm N}$ $\approx$42K. A field-induced spin-flop below $T_{\rm N}$ results in a switch from negative to positive magnetoresistance, with significant hysteresis causing butterfly-shaped resistance loops. In addition to reporting the properties of Fe$_{4.8}$AsTe$_2$, this work shows the importance of manipulating the individual magnetic sublattices in Fe$_{5-x}$GeTe$_2$ and motivates further efforts to control the magnetic properties in related materials by fine tuning of the Fermi energy or crystal chemistry.