Magnetic properties of AlFe₂B₂ and CeMn₂Si₂ synthesized by melt spinning of stoichiometric compositions

Abstract

By suppressing the growth of impurities, a melt spinning method was successfully applied to the synthesis of typical 1 : 2 : 2 layered CeMn 2 Si 2 and AlFe 2 B 2 compounds. X-ray diffraction analysis showed that CeMn 2 Si 2 and AlFe 2 B 2 had good purity and crystallized in ThCr 2 Si 2 -and AlFe 2 B 2 -type structures, respectively. The differences among three 1 : 2 : 2-type structures were also analyzed. The magnetic properties were investigated by magnetic measurements and electronic structure calculations. It was found that the Fe moment of AlFe 2 B 2 reaches 1.32 μ B at 5 K, which fits well with the calculated result of 1.44 μ B at 0 K, and that the isothermal magnetic entropy change reaches 7.2 J kg %1 K %1 at 5 T, which shows great potential for room-temperature refrigeration applications.

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

“…These procedures are contemplated to contribute to different antisite occupancies, producing variations in the 1-2-2 b-axis and in the associated (T-T) b-axis interatomic distances (Bond 1 inFigure 1).The (T-T) b-axis interatomic distance traverses the Al atom layer within the (ac)-plane, suggesting that Al and T atom antisite occupancy or Al-site vacancies could alter the Al layer spacing resulting in the distribution of the structural and magnetic properties observed for AlFe 2 B 2 . This conclusion is supported by, for example, the noted differences in T t reported for arc-melted (T t ~ 290 K) and melt-spun (T t = 312 K) samples of Al 1.2 Fe 2 B 2 nominal composition[24,25].…”

“…The role of specific 3d transition-metal substitution for Fe on the crystal structure and magnetic phase transition of AlFe 2 B 2 has been previously investigated [20][21][22][23][24]. Substitutions of Co and Mn are reported to lead to contraction and expansion along the c-axis, respectively, relative to the unmodified composition AlFe 2 B 2 ; both elemental additions were found to destabilize the compounds' ferromagnetism.…”

Effects of Al and Fe solubility on the magnetofunctional properties ofAlFe2B2

“…To date, a number of studies have investigated the effect of compositional modification on the structure, magnetism, and magnetocaloric response of AT 2 X 2 compounds (A = Al, Ga, Ge; T = Mn, Fe, Co, Ni; X = B, C) [5,7,[9][10][11][12][13][14]. Although the AT 2 X 2 family of materials can accommodate a broad range of 3d transition metals and main group elements, the parent compound, AlFe 2 B 2 retains the highest reported magnetic phase transition temperature (T t = 312 K) [5,12].…”

“…A range of nominal Fe:Al at.% ratios (0.66-2.0) and processing techniques have been employed in previous studies to produce the parent compound: AlFe 2 B 2 [5,10,12,15,16]. The chosen conditions for synthesis of unsubstituted AlFe 2 B 2 result in a large variation in structural properties and magnetic properties for the AlFe 2 B 2 (aka 1-2-2) phase [5,[7][8][9][10][11][12].…”

“…A range of nominal Fe:Al at.% ratios (0.66-2.0) and processing techniques have been employed in previous studies to produce the parent compound: AlFe 2 B 2 [5,10,12,15,16]. The chosen conditions for synthesis of unsubstituted AlFe 2 B 2 result in a large variation in structural properties and magnetic properties for the AlFe 2 B 2 (aka 1-2-2) phase [5,[7][8][9][10][11][12]. Levin et al investigated the effect of nominal starting composition and annealing on the phases present in Al:Fe:B alloys (x:2:2; x = 1.0, 1.1, 1.2), but at this time no study has correlated the intrinsic properties with chemistry for the 1-2-2 phase [15].…”