High-temperature ferromagnetism in Si1 − x Mn x (x ≈ 0.5) nonstoichiometric alloys

Ferromagnetism of MnxSi1-x(x ∼ 0.5) films grown in the shadow geometry by pulsed laser deposition method

“…To justify this explanation we have to suggest that in the upper layer, the effect of LT FM order on the Hall transport is similar to the case of bulk ε-MnSi, where AHE has the negative sign. 20,22 At the same time, we have to postulate that in the interfacial layer, the effect of the HT FM order on the Hall transport is similar to the case of DG films, 3 where the AHE of positive sign was reported 3 (the AHE of positive sign is observed also in amorphous Mn x Si 1-x alloys. 7,23 ) Evidently, in the two-layer SG grown film a partial compensation of negative and positive contributions ρ H (B) should be more pronounced at temperatures below the Curie temperature of the LT FM layer (T Cl ≈ 46 K); this compensation becomes more efficient with the film thickness increasing.…”

“…1 Recently we reported the HT FM appearance with T C ≈ 330 K in 70 nm thick Mn x Si 1-x (x ≈ 0.52-0.55) films grown on the Al 2 O 3 (0001) substrates by pulsed laser deposition (PLD) technique. 3,4 We argued that the observed HT FM has a defect-induced nature: it is due to formation of local magnetic moments on the Si vacancies inside the MnSi matrix and the strong exchange coupling between these moments mediated by spin fluctuations of itinerant carriers. 12 The Mn x Si 1-x films in 3,4 were deposited at a relatively slow deposition rate (∼2 nm/min) using PLD method in a conventional "direct" geometry (DG) when the surface of Al 2 O 3 (0001) substrate is exposed to the Mn-Si laser plume.…”

“…3,4 We argued that the observed HT FM has a defect-induced nature: it is due to formation of local magnetic moments on the Si vacancies inside the MnSi matrix and the strong exchange coupling between these moments mediated by spin fluctuations of itinerant carriers. 12 The Mn x Si 1-x films in 3,4 were deposited at a relatively slow deposition rate (∼2 nm/min) using PLD method in a conventional "direct" geometry (DG) when the surface of Al 2 O 3 (0001) substrate is exposed to the Mn-Si laser plume. Accordingly to atomic-force microscopy (AFM) measurements, the structure of thus grown films is mosaic, with the crystallite size ∼0.5-1 µm.…”

“…On the other hand, the Mn x Si 1-x (x≈0.5) thin layers grown on Si(001) or Al 2 O 3 (0001) substrates demonstrate the high-temperature (HT) ferromagnetism (FM) with the Curie temperature T c of the order of room temperature. [2][3][4] This fact is in contrast to the case of bulk ε-MnSi single crystal, where only the low-temperature (LT) FM was reported with T C ≈ 30 K. 8,9 The HT FM order at x 0.506 (that just corresponds to the single crystal ε-MnSi belonging to berthollides 9,10 ) was observed in the Mn x Si 1-x /Si(001) structures but at enough small Mn x Si 1-x film thickness less than one ε-MnSi monolayer. 2,11 This order is explained by the formation of c-MnSi phase with B2-like (CsCl) crystal structure stabilized with tetragonal distortion due to favorable lattice mismatch between the film and substrate.…”

“…[1][2][3][4][5][6][7] The perfect single crystal ε-MnSi with B20-type of structure possesses at low temperatures (≤ 30 K) intriguing magnetic and transport phenomena caused by formation of new magnetic quasiparticles -skyrmions (see Ref. 6 and references therein).…”