Papers by Keyword: Single-Domain

Abstract: Single-domain M-type Strontium Ferrite nanoparticles are prepared by the co-precipitation method. The crystallite size of the M-SrFe Nps is 58.1 nm, as determined by the XRD pattern. The SEM micrographs reveal the hexagonal morphology. M-SrFe Nps is depicted in EDS analysis. According to VSM characterization, the sample is a hard magnetic material with high coercivity. With its outstanding magnetic characteristics, hexaferrite is typically employed in permanent magnetic materials and recording devices. The band gap energy is determined to be 1.95 eV from the UV-DRS reflectance data using the Kubelka-Munk plot. The absorbed wavelength with the highest intensity peak in PL analysis is 629.9 nm. The TG-DTA investigations support the remarkable thermal stability of M-SrFe Nps. The resistivity of the sample, 0.312 Ωm is calculated using the four-probe method.

Abstract: We have systematically investigated the domain structures of Barium Hexaferrite (BaFe₁₂O₁₉) by means of a micromagnetic simulation under zero external magnetic field. A hexagonal-shaped and cylindrical-shaped models are used in this simulation with respect to the diameter variation from 50 nm to 600 nm. A transition domain structure is found from a single-domain (SD) to multi-domain (MD) at a certain diameter. The hexagonal-shaped occurs in diameter 430 nm and cylindrical-shaped in diameter 410 nm. Interestingly, the domain wall of MD structure exhibits a Bloch-wall type. The domain wall width is determined by full width half maximum (FWHM) method from the transverse magnetization component data. The domain wall width from simulation showed close to Kittel’s formula

Abstract: We report on the heteroepitaxial growth of 3C-SiC layers by Vapor-Liquid-Solid (VLS) mechanism on various α-SiC substrates, namely on- and off-axis for both 4H and 6H-SiC(0001), Si and C faces. The Si-Ge melts, which Si content was varied from 25 to 50 at%, were fed by 3 sccm of propane. The growth temperature was varied from 1200 to 1600°C. It was found that singledomain 3C-SiC layers can be obtained on 6H-SiC off and on-axis and 4H-SiC on-axis, while the other types of substrate gave twinned 3C-SiC material. As a general rule, one has to increase temperature when decreasing the Si content of the melt in order to avoid DPB formation. It was also found that twinned 3C-SiC layers form at low temperature while homoepitaxy is achieved at high temperature.

Abstract: The unidirectional solidification technology by a zone melting method was performed to obtain the large single domain YBCO. The interface morphology and chemical composition at the growth front of the YBCO crystal were investigated in order to make clear the growth characteristic of the YBCO crystal during melting growth by unidirectional solidification. It was found that YBCO crystal would cease growing when yttrium was depleted in the liquid phase at the YBCO crystal growth front. For maintaining the continuous growth of YBCO crystal, compositions of Y, Ba and Cu in raw samples have to be adjusted so as to make yttrium rich in the liquid phase at the YBCO crystal growth front during the melting growth process. It is very useful for the study on the mechanism of the YBCO crystal growth.

Abstract: Using the Vapor-Liquid-Solid mechanism in Ge-Si melts we have grown 3C-SiC layers on top of <0001>-oriented, Si face, 6H-SiC substrates. The surface morphology was free of spiral growth but highly step bunched. The 3C-SiC polytype was identified by micro- Raman spectroscopy and confirmed by low temperature photoluminescence. Electron backscattering diffraction mapping showed that the upper side of the layers is single-domain, i.e. that the 3C-SiC material displays only one in-plane orientation. Cross-sectional and planeview TEM investigations allowed detection of double positioning boundaries but only confined at the substrate/epilayer interface. The main additional defects found were stacking faults (SF) with a density of ~ 4.103 cm-1. Forming at the interface, they propagate through the epitaxial layer.