Structural, electronic and magnetic properties of the Mn54−xAl46Tix (x = 2; 4) alloys

The structural, electronic and magnetic behavior of the as-cast and annealed Mn52Al46Ti2 and Mn50Al46Ti4 alloys have been studied through electronic band structure calculations, X-ray diffraction and magnetic measurements in the temperature range 4-850 K and magnetic field up to 7 T. Band structure calculations show a preference for Ti atoms to occupy the Mn sites in the plane of Al atoms with their magnetic moments (−0.68 μB/Ti) coupled antiparallel relative to the Mn magnetic moments in the plane of Mn atoms (2.33 μB/Mn). The as-cast and annealed samples were phase mixtures with different values of the hard ferromagnetic τ phase content. Except the as-cast and annealed at 1050 °C Mn52Al46Ti2 alloys, all the analyzed samples include, along with the τ and γ2 phases, a soft κ phase (CsCl - structure type) with TC around 530 K. The best magnetic characteristics were obtained for Mn52Al46Ti2 alloy annealed at 470 °C for 6 h: MS = 116 A m2/Kg at 4 K and TC = 668 K, in good agreement with the values reported in the literature for the τ phase of the MnAl system. The effects of the composition and of the preparation route on the electronic and magnetic properties are discussed in comparison with the properties of Mn54Al46 parent alloy.