Magnetotransport properties of nonstoichiometric Si–Mn alloys with an excess of manganese relative to silicides Mn4Si7 and MnSi

Comparative examination of magnetotransport properties of nonstoichiometric Si 1– x Mn x alloys with roughly the same (δ х / x ≈ 7%) excess of Mn relative to silicides Mn 4 Si 7 and MnSi has been performed. Films of Si 1– x Mn x ( х ≈ 0.39 and 0.535) with a thickness of 60–70 nm have been fabricated by means of pulsed laser deposition on Al 2 O 3 (0001) substrates at a temperature of 340°С. It has been found that the excess of Mn produces the strongest effect on the Curie temperature in the case of MnSi ( Т С increases from 30 K to 300 K and higher), while no such effect is observed in Mn 4 Si 7 . This may be attributed to strong nonmagnetic disorder in Si 1– x Mn x with x ≈ 0.39 and the associated unusual behavior of negative magnetoresistance (NMR): The NMR varies linearly with magnetic field at В ≤ 1.3 T and exhibits almost no temperature dependence at T = 40–85 K.