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P. B?oński 《Surface science》2007,601(1):123-133
Trends in atomic multilayer relaxations, surface energy, electronic work function, and magnetic structure of several low-Miller-index surfaces of iron are investigated employing density functional theory total energy calculations. The calculated topmost layer relaxations reproduce well the experimental contractions and their variation with the surface crystallographic orientation, and surface roughness. The multilayer relaxation sequences correlate with the reduced coordination in surface layers and can be explained in terms of a simple electrostatic picture. The surface energies scale almost linearly with the surface roughness. They agree well with the experimental surface tensions and show a small anisotropy in agreement with predictions based on measurements for other metals. The equilibrium shape of a bcc Fe crystal is determined and discussed. The work function anisotropy is calculated and rationalized in terms of changes in the valence charge distribution. Significantly increased local magnetic moments of atoms in the surface region are determined. The correlation between the anisotropy of the surface magnetic moments and atomic coordination in the outermost layers is demonstrated to follow a simple rule. 相似文献
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M. Demand M. Hehn R.L. Stamps C. Meny K. Ounadjela 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):167-176
Growth, structural and magnetic properties of cobalt island structures grown by molecular beam epitaxy on 4 nm thick island
shaped Ru buffers are studied. The islands are characterized by a narrow distribution of sizes, and are separated on average
by spacing of around one hundred nanometers. Growth of the islands into continuous films is found to proceed in three well
defined stages, and corresponding magnetic behaviors are identified. The particles formed in the first stage of growth appear
to be similar in shape and size, and their magnetic behavior suggest the presence of superparamagnetism. Particles in the
second stage of growth are ferromagnetic and display a reorientation transition of their magnetization out of the film plane,
consistent with that seen in patterned magnetic dot arrays. Particles coalesce in the last stage of growth and magnetic properties
of continuous films are observed.
Received 24 August 2001 相似文献
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R. Torchio C. Meneghini S. Mobilio G. Capellini J. Alonso V. Turco Liveri A.M. Ruggirello 《Journal of magnetism and magnetic materials》2010,322(21):3565-3571
The magnetic response of nanometer sized Co nanoparticles (NP) prepared using reverse micelle solutions are presented. The use of complementary structural and morphological probes (like transmission electron microscopy, high resolution electron microscopy, X-ray absorption spectroscopy) allowed to relate the magnetic properties to the size, morphology, composition and atomic structure of the nanoparticles. All data agree on the presence of a core-shell structure of NPs made of a metallic Co core surrounded by a thin Co-oxide layer. The core-shell microstructure of NPs affects its magnetic response mainly raising the anisotropy constant. 相似文献
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Macroscopic fractal aggregates of cobalt are obtained by thermal evaporation of cobalt metal in an argon atmosphere and subsequent
deposition on a silicon substrate heated to 1000 K. It is established that the fractal structure is formed by diffusion-limited
aggregation of cobalt particles. The macroscopic fractal cobalt aggregates are ferromagnetic.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 556–558 (25 October 1997) 相似文献
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Liu XD Iimori T Nakatsuji K Komori F 《Physical review letters》2008,100(8):089601; author reply 089602
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利用纯度为995%的Al片进行阳极氧化,制成多孔氧化铝,通过两步纳米复合,制备了金属Co纳米孔洞模板.分别用透射电子显微镜(TEM)、X射线衍射仪(XRD)和振动样品磁强计(VSM)对样品进行了测试分析TEM观察的结果显示,模板孔洞分布均匀、局域有序,平均孔径为30nm左右,孔心距约为59nm;XRD测试的结果表明,模板是Co的多晶,并且具有明显的(002)取向;VSM测得模板的矫顽力为6164×104Am,比Co的块材有很大提高
关键词:
纳米孔洞模板
电化学
矫顽力 相似文献
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Y.M. Abbas S.A. Mansour M.H. Ibrahim Shehab.E. Ali 《Journal of magnetism and magnetic materials》2012
The structural and magnetic properties of the spinel ferrite system Co1+xFe2−2xSnxO4 (x=0.0–1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm−1 and 425 cm−1, which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. 相似文献
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This paper discusses experimental studies of the temperature dependence of the magnetic susceptibility, electrical conductivity,
and Seebeck coefficient of the compounds CoxTiSe2 (0.1⩽x⩽0.5), along with the structural behavior exhibited by these compounds. For Co0.5TiSe2, the observed temperature dependence of the magnetic susceptibility is characteristic of an antiferromagnet with a Néel temperature
of 510 K. The data obtained on the structural characteristics and physical properties of the intercalated phases are interpreted
using a model that assumes the formation of bands of localized states near the Fermi level.
Fiz. Tverd. Tela (St. Petersburg) 39, 1618–1621 (Sepember 1997) 相似文献
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Lirong Ren Lin He Chinping Chen Michael Wark Chunping Li Ping Che Lin Guo 《Journal of magnetism and magnetic materials》2007
Co-based (Co and Co3O4) nanoparticles were self-integrated into SiO2 nanotubes with a methodology based on the use of a Co salt as a template structure for the formation of SiO2 nanotubes. Within the confinement of tubular matrix of SiO2, the nanofibres of cobalt precursor, i.e., [Co(NH3)6](HCO3)(CO3)·2H2O, were treated in a H2 atmosphere with different parameters. With a sufficient reduction on the cobalt precursor, sphere-like Co-based nanoparticles are obtained, being well aligned in the interior space of the SiO2 nanotubes. With an insufficient reduction, platelet-like Co-based nanoparticles are formed, being arranged in a random manner inside the SiO2 nanotubes. The sufficiently reduced Co–SiO2 nanocomposite exhibits an open hysteresis loop in the low field region (<3 kOe) and a paramagnetic response in high field (>3 kOe) at 300 K. An observed wide separation between the zero-field-cooling (ZFC) and field-cooling (FC) curves over the whole temperature region has demonstrated a characteristic feature of ferromagnetism with a magnetically anisotropic barrier diverting the easy axis from the axis of the applied field. The predominant factor leading to this anisotropic potential barrier is attributed to the shape anisotropy native to the one-dimensional arrangement of Co-based nanoparticles within the tubular matrix, i.e. SiO2 nanotubes. 相似文献
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