Theoretical investigations of an influence of Ti on electronic structure and magnetic properties of half-metallic Fe2Mn1−xTixSi0.5Al0.5 alloys

• Half-metallic band gap is obtained for Fe2Mn1−xTixSi0.5Al0.5 for x≤0.375.
• The further increase of Ti content leads to a strong decrease of polarization ratio.
• The main carrier of magnetism of the compound is manganese.
• Total magnetic moment decreases almost linearly with increasing Ti content.

Ab-initio electronic structure calculations are carried out for quinternary Fe2Mn1−xTixSi0.5Al0.5 alloys basing on the density functional theory. When x=0, the alloy is a half-metallic ferromagnet with magnetic moment following the Slater–Pauling rule. Main carrier of magnetism of the alloy is manganese with the magnetic moment of about 2.5 μB. Replacement of Mn by Ti, changes its electronic and magnetic structure. Half-metallicity is present up to Ti concentration x=0.375. However, the further increase of Ti content leads to a strong decrease of electronic spin polarization. When the concentration of Ti increases, total magnetic moment strongly decreases. Fe magnetic moment, in the presence of titanium, changes its orientation into antiparallel in respect to the total magnetic moment and its absolute value increases with increasing Ti content. However, absolute value of Fe magnetic moment does not exceed 0.17 μB. Ti exhibits very weak spin polarization with magnetic moment not higher than 0.05 μB.