Magnetic and mechanical effects of Mn substitutions in AlFe2B2

Abstract

The mechanical and magnetic properties of the newly discovered MAB-phase class of materials based upon AlFe 2 B 2 were investigated. The samples were synthesised from stoichiometric amounts of all constituent elements. X-ray diffraction shows that the main phase is orthorhombic with an elongated b-axis, similar to AlFe 2 B 2 . The low hardness and visual inspection of the samples after deformation indicate that these compounds are deformed via a delamination process. When substituting iron in AlFe 2 B 2 with manganese, the magnetism in the system goes from being ferro-to antiferromagnetic via a disordered ferrimagnetic phase exhibited by AlFeMnB 2 . Density functional theory calculations indicate a weakening of the magnetic interactions among the transitions metal ions as iron is substituted by manganese in AlFe 2 B 2 . The Mn-Mn exchange interactions in AlMn 2 B 2 are found to be very small.

Thermal stability of the nanolayered Fe2AlB2 in nitrogen and argon atmospheres

“…The fact that neither the B‐FAB herein nor the dense samples studied in Ref. [8,10,11] were treated in HCl and show better high‐temperature stability supports this conjecture.…”

“…The thermal stability of bulk Mn 2 AlB 2 , 7,8 MoAlB, 9 and Fe 2 AlB 2 8,10,11 borides has been reported in argon (Ar), nitrogen (N 2 ), or vacuum atmospheres. Kota et al showed that bulk Mn 2 AlB 2 was stable up to ≈1380 K and decomposes into the binary boride MnB and Al‐rich phases above this temperature 7 .…”

“…Differential thermal analysis, quenching experiments, X‐ray diffraction (XRD), and scanning electron microscopy (SEM) showed evidence that bulk MoAlB samples are stable up to 1708 K and then decompose into MoB and Al in vacuum or inert atmospheres 9 . Bulk Fe 2 AlB 2 samples have been reported to be stable up to the 1440‐1520 K temperature range in He or Ar atmospheres 8,10,11 . Liu et al observed that substantial amounts of β‐FeB precipitated in bulk samples after annealing at ≈1510 K in an Ar atmosphere 11 .…”

Magnetron Sputtering of Nanolaminated Cr2AlB2

“…The formation of Cr 2 AlB 2 , CrB 2 and Al grains is also confirmed by the EDS maps in Figure 5b and their orientation relationship can be determined from the electron diffraction patterns. Thus, the Cr 2 AlB 2 (200), the CrB 2 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) and the Al (−220) reflections marked in Figure 7b-d coincide. These correspond to aligned lattices with spacings of 1.4315, 1.4860 and 1.4686 Å in the ideal structures, respectively.…”

“…This phase has been suggested as a potential material for magnetic refrigeration due to its magnetocaloric properties [10]. In contrast, Mn 2 AlB 2 is antiferromagnetic, while solid-solutions mixing Mn and Fe on the metal sites give a disordered ferrimagnetic phase [11]. In the Cr-Al-B system, three phases in the series (CrB 2 ) n CrAl with n = 1, 2, 3 have been synthesised [8].…”