Electronic structures and magnetocrystalline anisotropy energies of ordered Co1-xNix alloys: a first principles study

The electronic structures and magnetocrystalline anisotropy(MA) of ordered hexagonal close-packed(hcp) Co1-xNix alloys are studied using the full-potential linear-augmented-plane-wave(FLAPW) method with generalized gradient approximation(GGA).Great changes of magnetocrystalline anisotropy energy(MAE) are gained with different Ni compositions.Also,in-plane magnetocrystalline anisotropy is obtained for Co 15 Ni in which the Snoek’s limit is exceeded.It is found that the changes of the symmetry of the crystal field on Ni induce small variations in band structures around the Fermi level under different compositions,which plays an important role in modulating the magnetization direction,where the hybridization between Co-3d and Ni-3d orbits is of special importance in deciding the magnetocrystalline anisotropy of itinerant states.The rigid-band model is inapplicable to explain the evolution of magnetocrystalline anisotropy energy with Ni composition,and it is also inadequate to predict the magnetocrystalline anisotropy energy through the anisotropy of the orbital magnetic moment.     

Light scattering from anisotropic particles: propagation,localization, and nonlinearity

Plasmon resonances and extraordinary light scatterings of a nanoparticle with radial anisotropy are studied and summarized. The coupling between localized surface plasmons and far‐field quantities is discussed. It is found that the presence of radial anisotropy redistributes the localization of plasmons and also results in certain novel phenomena in the far zone, which provide the possibility of scattering control such as electromagnetic transparency, enhanced scattering cross section, etc. The nonlinear optical response is explored in order to yield deeper physical insight into the interaction between plasmons and incident light.     

Photoresponsive poly(methyl methacrylate)‐b‐azodendron block copolymers prepared by ATRP and click chemistry

A range of block copolymers (BCs) consisting of a linear poly(methyl methacrylate) (PMMA) block linked to an aliphatic polyester dendron functionalized with azobenzene moieties have been synthesized by sequential atom transfer radical polymerization (ATRP) and Click Chemistry. Two alkyne‐functionalized PMMA homopolymers with different molecular weights were obtained by ATRP and coupled to generations 2 to 4 of azodendrons bearing an azide group at the focal points. In the case of the azodendron with the highest generation number, the length of the flexible spacer attaching the cyanoazobenzene units to the dendron has also been modified. The coupling of both blocks and purity of BCs were checked by gel permeation chromatography, nuclear magnetic resonance, and infrared spectroscopy. The thermal transitions and liquid crystalline behavior of the BCs were investigated by differential scanning calorimetry and polarized‐light optical microscopy. A morphological study was carried out by transmission electron microscopy, using samples annealed at 115 °C. Photo‐induced anisotropy was induced in thin films of these materials after annealed at 115 °C. The highest stable birefringence values were obtained for the BCs bearing 8 and 16 azobenzene units in the dendritic block. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1538–1550, 2010     

Effect of molecular orientation on the fracture behavior of carbon black-filled natural rubber compounds

The fracture behavior of carbon black-filled natural rubber compounds, differing in filler content, was studied performing tensile tests in biaxial loading conditions, using a central notched cross-shaped specimen. The test consisted of two steps: a drawing step was initially performed loading the specimen in the direction parallel to the notch plane, up to different draw ratios, and then the specimen was loaded in the direction normal to the notch plane up to fracture. Using a fracture mechanics approach, the fracture toughness was evaluated as a function of the draw ratio applied in the drawing step. A correlation between the fracture phenomenology observed and molecular orientability and orientation was attempted. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1509–1515, 2010     

Description of the elastic deformation and degradation of elastic properties of dispersedly failing isotropic materials

A model is put forward for describing the elastic deformation of a quasi-homogeneous isotropic material capable of accumulating scattered microdamages during loading, which eventually leads to its total failure. The degree of damage of the material at a point is characterized by a centrosymmetric scalar function on the unit sphere, named the damage function, whose values depend on a dimensionless equivalent stress. This function is approximated by a fourth-rank tensor, which is used to construct a constitutive relation between stresses and strains in a differential form. By way of example, the elastic deformation of concrete and the degradation of its linearly elastic properties are described, and the basic three-dimensional sections of the corresponding strength surface are constructed. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 193–208, March–April, 2006.     

Magnetic anisotropy of liquid crystals based on lanthanide mesogenic complexes

The values of magnetic anisotropy of smectic A-phases for a number of lanthanide complexes (LH)₂LM(NO₃)₂, where M=Nd, Eu, Gd, Tb, Dy, Ho, and Er, and LH is a Schiff's base), were measured. These values are two orders of magnitude larger than those normally found for diamagnetic liquid crystals and are well correlated with magnetic birefringence constants and molecular mangetic anisotropy of nomesogenic lanthanide diketonates. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 694–697, April, 1999.     

Bit-array alignment effect of perpendicular SOMA media

One effective way to overcome the superparamagnetic limit of magnetic recording system is to reduce the grain number per bit at given signal-to-noise ratio (SNR) level by using uniformed media grains. The self organized magnetic array (SOMA) is designed to have uniform grains with perfect grain array structure. It is believed that high enough SNR with small number of grains per bit can be acheived. But in the engineering application, the recorded bit on SOMA media may align with the regular array at different locations and angles due to non-grain synchronized writing, skew angle, and circular track. This induces the bit-array alignment effect and degrades system performance of SOMA media. In this paper, the micromagnetic simulation results show that the bit array alignment effect causes large level SNR fluctuation on the same media. The SOMA media is not preferred to be used in the conventional recording configuration. It is only suitable for the configuration of patterned media.     

Fluorescence metrology of silica sol-gels - The effect of D2O and inorganic salts

We have developed a new method for measuringin- situ the growth of the nanometre-size silica particles which lead to the formation of sol-gel glasses. This technique is based on the decay of fluorescence polarisation anisotropy due to Brownian rotation of dye molecules bound to the particles. Results to date give near ?ngstrom resolution and demonstrate the feasibility of the approach both for providing industrial quality control and helping fundamental research. Our approach has several key advantages over traditional techniques for nanometre metrology, such as small angle X-ray and neutron scattering and electron microscopy. In this paper we present silica particle growth dynamics in a hydrogel as detected by two near-infrared dyes, the effect of adding D₂O on the hydrodynamic radius and the effect of salt addition.     

Faceting of monolayer domains

The formation of facets in domains of three monolayer systems, differing in molecular structure or headgroup charge, is observed by Brewster-angle microscopy under different experimental conditions. Arachidic acid forms faceted domains on increasing the pH of the subphase from pH 12.0 to 12.3 or by adding traces of cholesterol at pH 12.0. The degree of faceting is gradually varied in a mixture of 1-monopalmitoyl-rac-glycerol and 1-O-hexadecyl-rac-glycerol. The surface potentials of the pure substances were measured in order to determine the electrostatic forces in the mixture. Reversible faceting of domains of heptadecanoic acid methyl ester is observed within 2 °C near 30 °C. Faceting in monolayers is explained on the basis of fundamental forces that govern domain texture and shape, including line tension anisotropy and electrostatic repulsive forces. This explanation also accounts for the formation of dendrites along certain directions at domains of arachidic acid and the methyl ester. Received: 9 August 1999/Accepted in revised form: 24 August 1999