New functional nanocomposite FePt:C thin films with FePt underlayers were synthesized by noneptaxial growth. The effect of the FePt layer on the ordering, orientation and magnetic properties of the composite layer has been investigated by adjusting FePt underlayer thickness from 2 nm to 14 nm. Transmission electron microscopy (TEM), together with x-ray diffraction (XRD), has been used to check the growth of the double-layered films and to study the microstructure, including the grain size, shape, orientation and distribution. XRD scans reveal that the orientation of the films was dependent on FePt underlayer thickness. In this paper, the TEM studies of both single-layered nonepitaxially grown FePt and FePt:C composite L10 phase and double-layered deposition FePt:C/FePt are presented.
Nonepitaxially grown double-layered films were synthesized with a FePt: C composite layer on top of continuous FePt underlayer. The thickness of FePt was changed from 2 nm to 14 nm. Nanostructures, crystalline orientations and the effect of FePt underlayer on the ordering, orientation and magnetic properties of the thin films were investigated by transmission electron microscopy (TEM) and x-ray diffraction (XRD). XRD confirmed the formation of the ordered L10phase for 5 nm FePt: C film with FePt thickness decreased to 5 nm. TEM studies of FePt:C composite L10phase and double-layered deposition FePt:C/FePt were presented.
Alfalfa ( Medicago sativa L.) establishment is an effective strategy of managing desertification in arid regions; however, the course of artificial alfalfa grassland degradation remains poorly understood. Therefore, we investigated the dynamics of vegetation characteristics, soil edaphic factors, and rhizosphere microbial community structure in the course of artificial alfalfa grassland degradation. A space–for–time substitution approach was used to select nine alfalfa stands with different ages (1–50 years old) in the loess hilly region of northwest China. According to the plant diversity of vegetation and important value of alfalfa, the course of grassland degradation could be divided into three stages, artificial grassland (1–10 years), transitional grassland (10–30 years), and natural grassland (>30 years). With an increase in stand age, alfalfa productivity first increased, up to a maximum in the 7-year-old stand, and then decreased. Alfalfa was replaced as the dominant species by Stipa bungeana in the 50-year-old stand. Soil bulk density, total organic carbon, and major nutrient contents were the highest in the artificial grassland. Soil enzyme activity and the relative abundances of potentially beneficial microorganisms (e.g., Mortierella and Glomus) peaked in the transitional grassland. Soil water content and total porosity reached the maximum levels in the natural grassland. The species diversity indices of bacterial and fungal communities first increased and then decreased over time. Both microbial abundance and species diversity in the 0–20-cm soil layer were higher than in the 20–40-cm soil layer. Soil pH and catalase activity predominantly influenced vegetation characteristics, while total and available phosphorus contents were the major edaphic factors shaping rhizosphere microbial community structure. The results indicated that alfalfa establishment altered soil structure considerably, and improved soil fertility in the artificial grassland over the short term. Consequently, soil enzyme activity, microbial diversity, and potentially beneficial microorganisms in the rhizosphere increased during the transitional stage. Following considerable shifts in the soil environmental conditions, alfalfa was no longer the only dominant species and was eventually replaced by S. bungeana, leading to the establishment of a stable natural grassland system.
Nonepitaxially grown FePt (x)/FePt:C thin films were synthesized, where FePt (x) (x=2, 5, 8, 11, 14 nm) layers were served as underlayers and FePt:C layer was nanocomposite with thickness of 5 nm. The effect of FePt underlayer on the ordering, orientation and magnetic properties of FePt:C thin films has been investigated by adjusting FePt underlayer thicknesses from 2 nm to 14 nm. X-ray diffraction (XRD), together with transmission electron microscopy (TEM) confirmed that the desired L10 phase was formed and films were (001) textured with FePt underlayer thickness decreased less 5 nm. For 5 nm FePt:C nanocomposite thin film with 2 nm FePt underlayer, the coercivity was 8.2 KOe and the correlation length of FePt:C nanocomposite film was 67 nm. These results reveal that the better orientation and magnetic properties for FePt:C nanocomposite films can be tuned by decreasing FePt underlayer thickness.
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