Microwave Synthesis and Magnetocaloric Effect in AlFe2B2

Dallas K Mann; YiXu Wang; Jeanette D Marks; Geoffrey F Strouse; Michael Shatruk

doi:10.1021/acs.inorgchem.0c01731

Microwave Synthesis and Magnetocaloric Effect in AlFe₂B₂

Inorg Chem. 2020 Sep 8;59(17):12625-12631. doi: 10.1021/acs.inorgchem.0c01731. Epub 2020 Aug 13.

Authors

Dallas K Mann¹, YiXu Wang^{1

2}, Jeanette D Marks^{1

3}, Geoffrey F Strouse¹, Michael Shatruk^{1

4}

Affiliations

¹ Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.
² School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China.
³ Sarasota Military Academy, Sarasota, Florida 34236, United States.
⁴ National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States.

PMID: 32786726
DOI: 10.1021/acs.inorgchem.0c01731

Abstract

A promising magnetic refrigerant, AlFe₂B₂, has been prepared for the first time by microwave (MW) melting of a mixture of constituent elements. For comparison, samples of AlFe₂B₂ 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 AlFe₂B₂. Although an excess of Al has to be used to suppress the formation of ferromagnetic FeB, the other byproduct, Al₁₃Fe₄, is easily removed by acid treatment, affording phase-pure samples of AlFe₂B₂. Our analysis indicates that the equimolar Fe/B ratio typically used for the preparation of AlFe₂B₂ 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.