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Thin films of Si1xMnx were deposited on Al2O3 substrate using pulsed laser deposition(PLD)technique employing time-of-flight separation of the ejected particles with different laser fluence (E = 3.8–7.6 J/cm2). Magnetic properties of these films reveal that the variation in the laser fluence has engineered several magnetic phases in Si1xMnx films: high temperature (HT) ferromagnetic (FM) phase Si1xMnx(x = 0.51–0.52) with uniformly distributed Si vacancies, and the low-temperature (LT) FM phases MnSi and Mn4Si7 with Curie temperature ≤ 40 K. At small fluence, the mesoscopic size MnSi and Mn4Si7 crystallites are formed in the upper layer of Si1xMnx films with Si excess (x ≈ 0.4–0.5), yielding to inhomogeneous magnetic phase distribution along the film growth direction, while the high and optimal fluence has resulted in uniform distribution of the HT FM phase during the film growth. The XPS, magnetotransport and ferromagnetic resonance (FMR) measurements confirm the presence of several FM phases in the samples and the amplifying role of LT FM for films grown at E ≤4.4 J/cm2.

A set of thin film MnxSi1-x alloy samples with different manganese concentration x≈0.44−0.63 grown by the pulsed laser deposition (PLD) method onto the Al2O3 (0001) substrate was investigated in the temperature range 4–300 K using ferromagnetic resonance (FMR) measurements in the wide range of frequencies (View the MathML source) and magnetic fields (View the MathML source). For samples with x≈0.52−0.55, FMR data show clear evidence of ferromagnetism with high Curie temperatures View the MathML source. These samples demonstrate a complex magnetic anisotropy described phenomenologically as a combination of the essential second order easy plane anisotropy contribution and the additional fourth order uniaxial anisotropy contribution with easy direction normal to the film plane. The observed anisotropy is attributed to a polycrystalline (mosaic) structure of the films caused by the film-substrate lattice mismatch. The existence of extra strains at the crystallite boundaries initiates a random distribution of local in-plane anisotropy axes in the samples. As a result, the symmetry of the net magnetic anisotropy is axial with the symmetry axis normal to the film plane. The principal features of the observed anisotropy are explained qualitatively within the proposed microscopic model.

Silicon based alloys with Mn-ions are a potential candidate for the spintronics applications, as they exhibit complex electric and magnetic phenomena which can be effectively utilized as the integrated-circuit elements in the contemporary microelectronic technology. Though, The Si1-xMnx alloys shows high-temperature ferromagnetism at low Mn concentration x ~ 0.05 – 0.1, but the small solubility of Mn-ions in Si leads to the formation of MnSi1.7 nanoparticles,1 which drives the system in an inhomogeneous phase and makes it irrelevant for the technological applications. However, a high Mn concentration in the Si1-xMnx alloys screens the precipitation of different inhomogeneous magnetic phases with high Curie temperature (TC).2 In this context, a set of thin films of Si1-xMnx (x = 0.44 – 0.57) alloy were prepared by the pulsed laser deposition technique on Al2O3 (0001) substrate. We have found room temperature ferromagnetism and a large magnetic moment for the Si0.43Mn0.57 film as compared to the rest of samples. But, surprisingly, the TC (as well as the moment) of Si0.43Mn0.57 film drastically decreases from 300 K to ~ 40 K as the Mn-ion concentration was increased in the film through the ion implantation process. In contrast, the stoichiometric film Si0.5Mn0.5 exhibits a huge increase in the magnetic moment by one-order in magnitude after ~ 2% Mn-ion implantation. The TC of the stoichiometric film also increases from 50 K to 300 K with the increase in the Mn-ion concentration.

The structural, transport, and magnetic characteristics of polycrystalline MnxSi1 – x (x ≈ 0.51–0.52) films grown by pulsed laser deposition onto Al2O3(0001) substrates when the low-energy components are deposited owing to collisions with the atoms of the buffer gas have been studied in the “shadow” geometry. The magnetization of these films is determined by two ferromagnetic phases—the high-temperature phase with the Curie temperature TC ≈ 370 K and the low-temperature one with TC ≈ 46 K. The anomalous Hall effect changes sign from positive to negative with a decrease in temperature. The sign change occurs in the temperature range of 30–50 K; the specific value of this temperature depends on the thickness of the MnxSi1–x film. The results can be interpreted in terms of the structural self-organization related to the formation of two layers in the course of film growth. These layers have nearly the same chemical composition but significantly differ in the shapes and sizes of crystallites. This leads to a drastic difference in the values of TC and in the value and the sign of the anomalous Hall effect for such layers.

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The results of a comprehensive study of magnetic, magneto-transport and structural properties of nonstoichiometric MnxSi1-x (x=0.51-0.52) films grown by the Pulsed Laser Deposition (PLD) technique onto Al2O3(0001) single crystal substrates at T = 340 C are present. A highlight of used PLD method is the non-conventional ("shadow") geometry with Kr as a scattering gas during the sample growth. It is found that the films exhibit high-temperature (HT) ferromagnetism (FM) with the Curie temperature TC ~ 370 K accompanied by positive sign anomalous Hall effect (AHE); they also reveal the polycrystalline structure with unusual distribution of grains in size and shape. It is established that HT FM order is originated from the bottom interfacial self-organizing nanocrystalline layer. The upper layer adopted columnar structure with the lateral grain size >50 nm, possesses low temperature (LT) type of FM order with ТС ~ 46 K and contributes essentially to the magnetization at T < 50 K. Under these conditions, AHE changes its sign from positive to negative at T < 30K. We attribute observed properties to the synergy of distribution of MnxSi1-x crystallites in size and shape as well as peculiarities of defect-induced FM order in shadow geometry grown polycrystalline MnxSi1-x (x~0.5) films.

The paper reports on the comprehensive study of properties of nonstoichiometric Si1−xMnx alloys slightly enriched in Mn (x≈0.51–0.55) as compared to the stoichiometric monosilicide MnSi. Mosaic type Si1−xMnx films 55–70 nm in thickness were produced by the pulsed laser deposition (PLD) method onto the single crystalline Al2O3 substrates at 340 °C. The Curie temperature TC in nonstoichiometric Si1−xMnx (x≈0.52–0.55) films exceeds room temperature, while in their stoichiometric counterpart, MnSi, the TC value does not exceed ≈30 К. The consistent data on anomalous Hall effect and transverse Kerr effect prove the global character of ferromagnetic (FM) order caused by magnetic defect formation rather than the presence of FM clusters. Аt Mn content x≤0.55, the magnetization data testify to a good homogeneity in the distribution of magnetic defects without their segregation: variations of the saturation magnetization Ms do not exceed 6% in the temperature range T=10–100 К and are well described by the Bloch law. It is also revealed that textured high-quality Si1−xMnx films with x≈0.52 and ТС~300 К could be formed by PLD method in the “shadow” geometry (at lower energy of deposited atoms).