Lattice-driven magnetic transitions in Al(Fe,T)2X2 compounds

Date
2019-03-06
Authors
Lejeune, B. T.
Jensen, Brandt
Barua, R.
Stonkevitch, E.
McCallum, R. W.
Kramer, Matthew
Lewis, L. H.
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Ames Laboratory
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Abstract

Systematic trends connect detailed composition, lattice parameters and magnetic transition temperatures in the ferromagnetic intermetallic compound AlT2X2 with the Mn2AlB2-type crystal structure, where T = Mn, Fe, Ni, Co and X = B, C. Data were derived from both literature reports and from experiments performed on synthesized samples (T = (Fe1−xNix)2, x = 0, 0.05, 0.1; X = (B0.9C0.1)2). It is observed that compositional variation alters specific bonds responsible for the magnetic phase transition response, which ranges from 200 K ≤ Tt ≤ 310 K. Elemental composition that provides changes in the c-axis length and the associated (T-T)c-axis interatomic distance contribute the largest bonding effects to magnetic phase transition temperature Tt, alterations. Overall, these results are attributed to the dependence of Tt on the specifics of the Fe sublattice occupancy, electronic state and T-T bonding. In contrast, Tt is found to be largely independent of the (b/a) axial ratios and the associated (T-X)b-axis/(T-X)(ac)-plane interatomic distance ratios, indicating that interatomic interactions along the a-axis have little effect on the Tt.

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Magnetic materials, Metals, Magnetocaloric, AlFe2B2, Rare-earth-free
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