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41.
The effect of ultrathin Fe underlayer on the strong in-plane magnetization of FePt magnetic thin film was investigated. This FePt thin film could be attained using the ultrathin Fe underlayer with 1 nm thickness. The in-plane coercivity of FePt film with 20 nm thickness grown on ultrathin Fe underlayer was high up to 7400 Oe. However, its out-of-plane coercivity was extremely low to 350 Oe compared to those of FePt thin films in other conventional studies. This result indicates that FePt thin film was strongly in-plane magnetized by ultrathin Fe underlayer. The strong ordering phase transformation kinetics and the high texturing to in-plane direction of the FePt thin film by ultrathin Fe underlayer were confirmed by Kinetics Monte Carlo (KMC) simulation and XRD measurement result, respectively. It is also supposed that they are associated with the reduction of an interface free energy between the film and the substrate with an introduction of ultrathin underlayer. 相似文献
42.
Katsuhiko Nishimura Wayne D. HutchisonYuta Tajiri Yosikazu IsikawaKeisuke Sato Koichi Kindo 《Physica B: Condensed Matter》2011,406(11):2281-2283
Magnetization measurements were carried out on Pr1−xGdxNi single crystals for x=0.1, 0.2, 0.3 and 0.4 using pulsed magnetic fields up to 55 T and at 4.2 K. For the data observed along the c-axis there are clear indications of transitions, of the combined system of Pr and Gd moments, from a ferrimagnetic to a ferromagnetic state. The observed saturation magnetizations at 55 T and intermediate magnetizations at 1 T were well modeled assuming ferro- and ferri-magnetic structures, respectively. 相似文献
43.
Stefan Buschhorn Frank Brüssing Radu Abrudan Hartmut Zabel 《Journal of synchrotron radiation》2011,18(2):212-216
A new set‐up is presented to measure element‐selective magnetization dynamics using the ALICE chamber [Grabis et al. (2003), Rev. Sci. Instrum. 74 , 4048–4051] at the BESSY II synchrotron at the Helmholtz‐Zentrum Berlin. A magnetic‐field pulse serves as excitation, and the magnetization precession is probed by element‐selective X‐ray resonant magnetic scattering. With the use of single‐bunch‐generated X‐rays a temporal resolution well below 100 ps is reached. The ALICE diffractometer environment enables investigations of thin films, described here, multilayers and laterally structured samples in reflection or diffuse scattering geometry. The combination of the time‐resolved set‐up with a cryostat in the ALICE chamber will allow temperature‐dependent studies of precessional magnetization dynamics and of damping constants to be conducted over a large temperature range and for a large variety of systems in reflection geometry. 相似文献
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45.
L.H. Kong R.R. ChenT.T. Song Y.L. Gao Q.J. Zhai 《Journal of magnetism and magnetic materials》2011,323(24):3285-3289
The magnetic properties and the annealing process of Fe78Zr7B15 amorphous ribbons are investigated by X-ray diffraction (XRD), differential scanning calorimetry, and vibrating sample magnetometer. The fully amorphous structure of the as-quenched ribbons is confirmed by the XRD pattern. The Curie temperature and the saturation magnetization Ms of the ribbons are 305 °C and 124.3 emu/g, respectively. Annealing at 550 °C can result in an increase in Ms with annealing time due to the increasing crystallized volume fraction of α-Fe phase. The optimized annealing process is established at 550 °C for 20-30 min with maximum Ms of 146.6 emu/g. The morphology of the ribbons annealed at 550 °C is observed by scanning electron microscopy, showing that nanocrystalline α-Fe grains are dispersed in an amorphous matrix. 相似文献
46.
Barium ferrites substituted by Mn-Sn, Co-Sn, and Mn-Co-Sn with general formulae BaFe12−2xMnxSnxO19 (x=0.2-1.0), BaFe12−2xCoxSnxO19 (x=0.2-0.8), and BaFe12−2xCox/2Mnx/2SnxO19 (x=0.1-0.6), respectively, have been prepared by a previously reported co-precipitation method. The efficiency of the method was refined by lowering the reaction temperature and shortening the required reaction time, due to which crystallinity improved and the value of saturated magnetization increased as well. Low coercivity temperature coefficients, which are adjustable by doping, were achieved by Mn-Sn and Mn-Co-Sn doping. Synthesis efficiency and the effect of doping are discussed taking into account accumulated data concerning the synthesis and crystal structure of ferrites. 相似文献
47.
Saurabh SahuRaj Kumar Dutta 《Journal of magnetism and magnetic materials》2011,323(7):980-987
A novel hybrid nanostructured material comprising superparamagnetic magnetite nanoparticles (MNPs) and pectin was synthesized by crosslinking with Ca2+ ions to form spherical calcium pectinate nanostructures, referred as MCPs, which were typically found to be 100-150 nm in size in dried condition, confirmed from transmission electron microscopy and scanning electron microscopy. The uniform size distribution was revealed from dynamic light scattering measurement. In aqueous medium the MCPs showed swelling behavior with an average size of 400 nm. A mechanism of formation of spherical MCPs is outlined constituting a MNP-pectin interface encapsulated by calcium pectinate at the periphery, by using an array of characterization techniques like zeta potential, thermogravimetry, Fourier transformed infrared and X-ray photoelectron spectroscopy. The MCPs were stable in simulated gastrointestinal fluid and ensured minimal loss of magnetic material. They exhibited superparamagnetic behavior, confirmed from zero field cooled and field cooled profiles and showed high saturation magnetization (Ms) of 46.21 emu/g at 2.5 T and 300 K. Ms decreased with increasing precursor pectin concentrations, attributed to quenching of magnetic moments by formation of a magnetic dead layer on the MNPs. 相似文献
48.
In this study, effect of lanthanum substitution on the phase composition, lattice parameters and magnetic properties of barium hexaferrite has been studied in samples synthesized in ammonium nitrate melt. Samples, prepared with different lanthanum amount and having various initial Fe/(Ba+La) ratios in between 12 and 2 {(Ba1−xLax)·n Fe2O3, where 0≤x≤1 and 1≤n≤6)}, are sintered at temperatures from 800 to 1200 °C. The lattice parameters, both a and c, decreases with increasing La amount which results in a decrease of the unit cell volume. The scanning electron microscope micrographs show that the pure and La-substituted sample with x=0.3, both calcinated at 1000 °C, have grain sizes smaller than 1 μm. The coercivities of the La-substituted samples increase with increasing La amount and reaches to a maximum value of 5.73 kOe, when x=0.3. Sintering at higher temperatures (above 1000 °C) decreases the coercivity, resembling a transition from single to multi-domain behavior of the particles, while saturation magnetization of the samples continues to increase due to the increasing grain size. Magnetization measurements of the samples prepared with different Fe/(Ba+La) molar ratios, n's, revealed that the specific saturation magnetization slightly increases with decreasing n, while coercivities fluctuates around 5.5 kOe. However, a sharp increase in the saturation magnetization has been observed in the sample having n=1 and washed in HCl. It was measured as 59.2 emu/g at 15 kOe, which is higher than that of the pure sample (57.5 emu/g). Thus, the magnetic parameters are optimized in the sample Ba0.7La0.3Fe12O19 so as to maximize both coercivity and specific saturation magnetization in the HCl-washed sample synthesized by starting with an unusually low Fe/(Ba+La) molar ratio of 2 (or n=1). 相似文献
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50.
A facile method to synthesize magnetic polymer nanospheres with multifunctional groups 总被引:1,自引:0,他引:1
Xiaojuan Zhang Wei JiangYuanfeng Ye Zhiqiang FengZhendong Sun Fengsheng LiLingyun Hao Jianjun Chu 《Journal of magnetism and magnetic materials》2011,323(11):1440-1444
Magnetic poly(styrene methyl methacrylate)/Fe3O4 nanospheres with ester groups were prepared by a modified one-step mini-emulsion polymerization in the presence of Fe3O4 ferrofluids. The effects of monomer dose, surfactant content, ferrofluid concentration and initiator content on the particle characteristics such as the size, morphology and magnetic properties were investigated by Fourier-transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis and vibrating sample magnetometer. The results indicated that magnetic nanospheres were superparamagnetic with high saturation magnetization of 51.0 emu/g and corresponding magnetite content of 61.5 wt%. Subsequently, magnetic nanospheres with carboxyl and amino groups were also obtained by hydrolysis and ammonolysis reaction. These magnetic nanospheres with multifunctional groups have biomedical applications. 相似文献