Obtaining Hexagonal MnSi Crystals by Alumothermal Reduction of Manganese(IV) Oxide

For the first time, hexagonal crystals of MnSi manganese silicide with a length of up to 2 mm and a diameter of up to 150 μm were synthesized by the method of alumothermal reduction of manganese(IV) oxide from a reaction mixture of MnO + Si + Al. Inclusions of the secondary phase of a solid solution of silicon in manganese aluminide of the composition (Mn, Si)Al were found on the surfaces of the faces of hexagonal crystals. The synthesized material based on MnSi hexagonal crystals is paramagnetic at room temperature. X-ray phase analysis showed that the MnSi phase is dominant in the synthesized samples. The obtained alloys also have different magnetic properties, for example: a sample synthesized from a reaction mixture of MnO + Si + Al at room temperature is paramagnetic, while samples obtained from a reaction mixture of MnO + SiO + Al containing a small number of secondary phases at room temperature exhibit weak ferromagnetic properties.