Effect of Ti substitution on alpha and beta phase formation and properties in Mn50-xTixBi50 alloys

MnBi intermetallic compound is a magnetic material with many unusual properties of interest for different applications such as rare-earth-free permanent magnets, spintronics and magnetic refrigeration. In this work the effect of Ti substitution on formation and magnetic properties of alpha and beta phases is investigated in Mn50-xTixBi50 polycrystalline bulk samples (x = 0-10). Two preparation techniques are compared: powder metallurgy and rapid quenching from the melt. A ternary metastable phase can be easily quenched from the melt, while powder metallurgy is not effective in promoting the incorporation of Ti into the MnBi lattice. The as-quenched Mn(Ti)Bi phase is non-magnetic at room temperature and it is fully transformed into the alpha-phase upon mild annealing. The samples magnetisation can be greatly increased by magnetic field annealing, due to the development of a preferential orientation in the alpha-phase crystals.