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

Abstract

Comparative examination of magnetotransport properties of nonstoichiometric Si_1–xMn_x alloys with roughly the same (δх/x ≈ 7%) excess of Mn relative to silicides Mn₄Si₇ and MnSi has been performed. Films of Si_1–xMn_x (х ≈ 0.39 and 0.535) with a thickness of 60–70 nm have been fabricated by means of pulsed laser deposition on Al₂O₃ (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 Mn₄Si₇. This may be attributed to strong nonmagnetic disorder in Si_1–xMn_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.