Hirt Sarah, Yuan Fang, Mozharivskyj Yurij, Hillebrecht Harald
Institut für Anorganische und Analytische Chemie, Albert-Ludwigs-Universität , Albertstraße 21, D-79104 Freiburg, Germany.
Department of Chemistry and Chemical Biology, McMaster University , Hamilton, Ontario L8S 4M1, Canada.
Inorg Chem. 2016 Oct 3;55(19):9677-9684. doi: 10.1021/acs.inorgchem.6b01467. Epub 2016 Sep 13.
AlFeB and AlFeCoB (x = 0-0.30) were synthesized from the elements in three different ways. The samples were characterized by powder X-ray diffraction, Rietveld refinements, energy-dispersive X-ray spectroscopy, and magnetic measurements. Using Al flux the formation of AlFeB single crystals is preferred. Arc melting enables the substitution of ∼6% Co. This substitution of Fe by Co decreases the Curie temperature T from 290 to 240 K. The highest Co substitution up to 15% is achieved by spark plasma sintering (SPS). T is reduced to 205 K. In all cases an excess of Al is necessary to avoid the formation of ferromagnetic FeB. AlFeCo is the common byproduct. T and the cobalt content are linearly correlated. The transition paramagnetic-ferromagnetic remains sharp for all examples. The magnetic entropy change of the Co-containing samples is comparable to AlFeB. SPS synthesis yields, in short reaction times, a homogeneous and dense material with small amounts of paramagnetic AlFeCo as an impurity, which can serve as sinter additive. These properties make AlFeCoB a promising magnetocaloric material for applications between room temperature and 200 K.
