Microwave Synthesis and Magnetocaloric Effect in AlFe₂B₂

Abstract

A promising magnetic refrigerant, AlFe 2 B 2 , has been prepared for the first time by microwave (MW) melting of a mixture of constituent elements. For comparison, samples of AlFe 2 B 2 have been also prepared by arc-melting, traditionally used for the synthesis of this material, and by induction (RF) melting, which was used in the very first report on the synthesis of AlFe 2 B 2 . Although an excess of Al has to be used to suppress the formation of ferromagnetic FeB, the other byproduct, Al 13 Fe 4 , is easily removed by acid treatment, affording phase-pure samples of AlFe 2 B 2 . Our analysis indicates that the equimolar Fe/B ratio typically used for the preparation of AlFe 2 B 2 might not provide the best synthetic conditions, as it does not account for the full reaction stoichiometry. Furthermore, we find that the initial Al/Fe loading ratio strongly influences magnetic properties of the sample, as judged by the range of ferromagnetic ordering temperatures (T C = 280−293 K) observed in our experiments. The T C value increases with the decrease in the Al/Fe ratio, due to the change in the Al/Fe antisite disorder. The use of the same Al/Fe loading ratio in the arc-, RF-, and MW-melting experiments leads to samples with a more consistent T C of 286−287 K and similar values of the magnetocaloric effect.

Exploring Doping Effects on Magnetocaloric, Magnetoelastic, and Magnetostriction Properties of Fe2AlB2: A First-Principles Study

“…Among the MAB compounds, Fe 2 AlB 2 exhibits interesting magnetic properties, including magnetic anisotropy and room-temperature magnetism, making it a promising candidate for magnetic refrigeration applications. − It has been previously shown that Fe 2 AlB 2 demonstrates itinerant magnetism. − The saturation magnetization at temperatures ≤50 K ranges from 0.7 to 1.60 μ B /Fe atom, ,− while the Curie temperature, T C , falls within the range of 272 to 320 K, ,− indicating a second-order magnetic transition around room temperature from a low-temperature ferromagnetic state to a high-temperature paramagnetic state. − ,, Moreover, bulk Fe 2 AlB 2 exhibits soft magnetic behavior with negligible remanence and coercivity. ,, However, due to its highly anisotropic crystal structure, Fe 2 AlB 2 single crystals display pronounced anisotropic magnetic properties. Fe 2 AlB 2 exhibits a reversible MCE near room temperature, characterized by a second-order magnetic transition, without experiencing cracking or hysteresis losses. ,,, The isothermal entropy change Δ s T and the indirectly determined adiabatic temperature change Δ T ad in Fe 2 AlB 2 are reported to be in the range of 1.3–4.4 J/(kg K) ,,,,,, and 1.0–1.8 K , at a magnetic field change of 2 T, respectively.…”

Polar Layered Intermetallic LaCo2P2 as a Water Oxidation Electrocatalyst

“…Despite its excellent performance in the alkaline electrocatalytic OER, AlFe 2 B 2 is not stable under acidic conditions. − In contrast, many ternary phosphides with related layered structures (Figure b) are known to exhibit high stability toward acids . Building on this knowledge, we have decided to explore the use of such structures in both acidic and alkaline water oxidation.…”

Effect of magnetocrystalline anisotropy on magnetocaloric properties of AlFe$_{2}$B$_{2}$ compound

“…In recent years, AlFe 2 B 2 has attracted much attention for future refrigeration with earthabundant elements, room-temperature magnetic transitions, and strong magnetocrystalline anisotropy energy. [17][18][19][20][21] AlFe 2 B 2 has an orthorhombic layered crystal structure with a space group Cmmm as depicted in Figure 1. The Fe and B layers form a zigzag chain in the ac plane.…”