Structure-Property Correlations in Sb, Ge, and Ga Doped AlFe$_2$B$_2$ for Magnetocaloric Applications

TL;DR

This study explores how doping AlFe$_2$B$_2$ with Sb, Ge, and Ga alters its magnetic and magnetocaloric properties, revealing specific effects on phase composition, Curie temperature, magnetization, and entropy change relevant for cooling applications.

Contribution

It provides new insights into how different dopants influence the magnetic and magnetocaloric behavior of AlFe$_2$B$_2$, aiding the design of tailored magnetocaloric materials.

Findings

Curie temperature increases with doping

Magnetic entropy change varies significantly with dopants

Ge doping maintains the relative cooling power

Abstract

This study investigates the effects of Sb, Ge, and Ga doping in AlFe$_2$B$_2$ on magnetic and magneto-caloric properties. Samples of AlFe$_2$B$_2$ and AlFe$_{1.9}$M$_{0.1}$B$_2$ (M= Ge, Ga and Sb) with 20\% excess Al were synthesized by arc melting, and the powder processed were investigated for their phase constituents, microstructure, magnetic and magneto-caloric effect. The parent compounds prepared showed the AlFe$_2$B$_2$ phase with a FeB secondary phase. However, in Sb and Ga-doped samples, an additional impurity phase, Al$_{13}$Fe$_4$, was observed apart from FeB, while in Ge-doped, only the AlB$_2$ impurity phase was present. The Curie temperature of AlFe$_2$B$_2$ is 277 K, increasing with Sb, Ge, and Ga doping to 287\,K, 297\,K, and 296\,K, respectively. The magnetization ($M$) is also higher with Ge and Ga addition in the 100-300\,K range; however, with Sb doping, the $M$ decreases significantly compared to parent AlFe$_2$B$_2$. The magnetic entropy change under 2\,T reached 2.93 JKg$^{-1}$K$^{-1}$ near 274\,K in AlFe$_2$B$_2$, which decreases to 2.53 JKg$^{-1}$K$^{-1}$ and 1.92 JKg$^{-1}$K$^{-1}$ with Ge and Ga, respectively. With Sb doping, the MC change was affected dramatically to 0.32 JKg$^{-1}$K$^{-1}$. However, the relative cooling power of Ge doped is the same as that of parent AlFe$_2$B$_2$. This research advances the understanding of the relationship between doping elements and magnetic properties in AlFe$_2$B$_2$ and opens pathways for designing magneto-caloric materials with tailored magnetic characteristics.