Stress and magnetic field-dependent Young's modulus in single crystal iron-gallium alloys

The variability in Young's modulus of single crystal iron-gallium (Galfenol) alloys having 16, 17.5, 19, 24.7 and 29 at% gallium is investigated using experiments and simulations. Some of these alloys showed more than 60% change in Young's modulus along the 〈1 0 0〉 directions on varying their magnetization and stress states compared to their modulus at magnetic saturation. A function, ΔE(σ,H), is defined such that the variability of modulus is bound between 0% and 100%. The observations are related to the inherent magnetomechanical coupling in the material. An energy-based non-linear constitutive model is used to predict the variable modulus in Galfenol as a continuous function of stress and magnetic field. Model predictions showed good correlation with experimental results.     

Domain structures of Nd13Fe80B7 magnets during HDDR process

The domain structures of Nd13Fe80B7 alloy at different stages of the HDDR process have been revealed using a magnetic force microscope. In the as-cast samples, the columnar crystals with easy axis perpendicular to one another are clearly characterized by their different domain structures. For the insufficient and sufficient HD treatment, an obvious change of domain structure occurs, which is related to the variation of composition and crystalline microstructure during the HD process. And for the samples after sufficient DR processing, it is confirmed that the configuration of the columnar crystals is retained by the detected domain structures.     

Stability of the magnetic domain structure of nanoparticle thin films against external fields

We investigate the effect of external magnetic fields on the magnetic structure of thin films from magnetic nanoparticles (MNP) with dipolar interaction. Such fields are present, for example, if samples are scanned with magnetic probes. Numerical simulations and experimental magnetic force microscopy (MFM) studies are presented. Numerically, we have calculated the magnetization pattern of single-layer and multilayer MNP thin films. The calculations show that unperturbed single-layer MNP films have an in-plane orientation of the magnetization with a flux-closure-domain pattern. An external field generated by a point dipole above the film induces locally an out-of-plane configuration of the magnetization. In the corresponding MFM images, the domain pattern in the film is erased and a stripe-like contrast enhancement at the edges appears. Multilayer films are found to be more robust against external fields than monolayers.     

壳核型磁性纳米纤维素微球的超声制备及表征

以纳米级的Fe3 O4液体作为磁核 ,在非水体系的纤维素DMAc(N N二甲基乙酰胺 ) /LiCl溶液中 ,使用包埋法 ,在超声波的辅助下制备得到了纳米尺度的壳核型磁性纤维素微球 .利用FT IR、XRD及AFM/MFM (原子力显微镜 /磁场力显微镜 )对得到的磁性微球进行了表征 ,证实该微球由磁性的核与纤维素的壳组成 ,微球大小为 30～ 5 0nm ,且具有良好的分散性 .并研究了超声条件对磁性微球尺寸的影响 .     

Interfacial morphology and domain configurations in 0-3 PZT-Portland cement composites

Cement-based piezoelectric composites have attracted great attention recently due to their promising applications as sensors in smart structures. Lead zirconate titanate (PZT) and Portland cement (PC) composite were fabricated using 60% of PZT by volume. Scanning Electron Microscope and piezoresponse force microscope were used to investigate the morphology and domain configurations at the interfacial zone of PZT-Portland cement composites. Angular PZT ceramic grains were found to bind well with the cement matrix. The submicro-scale domains were clearly observed by piezoresponse force microscope at the interfacial regions between the piezoelectric PZT phase and Portland cement phase, and are clearer than the images obtained for pure PZT. This is thought to be due to the applied internal stress of cement to the PZT ceramic particle which resulted to clearer images.     

Magnetic measurements of Fe-Ni-Nb-B and Fe-Co-Mo-Cu-B in the vicinity of the Curie temperature

The study of the transition between ferromagnetic and paramagnetic states has been investigated on selected metallic glass systems based on Fe-Ni-Nb-B and Fe-Co-Mo-Cu-B with T_C close to room temperature. Samples in the form of ribbons were prepared by planar flow casting and magnetostriction in parallel and perpendicular directions and saturation magnetostrictions have been determined on these samples in as-cast states together with hysteresis loops. In addition, a magneto-optic device for dynamic domain observation has been used for observation of domain structure. Magnetostriction measurements using direct method of measurement show the decrease of saturation magnetostriction towards zero upon approaching T_C. In paramagnetic state the field dependencies of magnetostriction in parallel and perpendicular configurations exhibit a linear dependence on the external magnetic field. In the transition region of temperatures the dependencies are a combination of ferromagnetic and paramagnetic field dependencies. The coercivity H_C in the materials investigated exhibits values below 20 A/m. The observed magnetic domains are typical for this class of amorphous alloys. The polarization in paramagnetic state increases gradually with increase in magnetizing field, reflecting the increasing amount of polarized regions.     

磁力显微镜对相分离锰氧化物薄膜中反铁磁绝缘相融化的成像

用自制磁力显微镜研究了一个受各向异性应变的锰氧化物薄膜中的相分离以及由磁场导致的从反铁磁绝缘相到铁磁金属相的转变．磁力显微镜图片显示,在0 T这两种竞争的相就已经共存,且两种相 的畴呈非常明显的各向异性的条状分布,这可以定性解释输运上的各向异性．在2.1 T 以上,反铁磁绝缘相逐渐转变为铁磁金属相,并在3.2 T时结束．当去掉磁场时铁磁金属相能够保持．     

In situ magnetic hysteresis measurement of magnetic tips in magnetic force microscope

In situ magnetic hysteresis measurements of magnetic tips in a magnetic force microscope (MFM) are demonstrated using alternating gradient force magnetometry. The measured magnetic moments of MFM tips are estimated in the range from 10⁻⁶ to 10⁻⁵ emu by this technique and the whole MFM tips in cantilevers are considered to be measured from the value of measured magnetic moments. The relationship between the magnetic hysteresis loops of MFM tips and those of coated magnetic films is discussed.     

AFM observations of latent fission tracks on surfaces: amorphous SiO2 and quartz

Preliminary results of a systematic AFM experimental investigation of the surface ‘track’ effects produced by the passage of fission fragments from a californium (²⁵²Cf) source into amorphous SiO₂ and quartz are described. Fission fragments from the source were collimated using a 10 μm thick aluminum foil and comprised fragments with the usual binary distribution of energies—light and heavy—79.4 and 103.8 MeV. Irradiations and AFM measurements were carried out in air at normal room temperature and pressure. Remarkably high sputtering yields/fragment were discovered, and in the case of crystalline quartz the ejecta was found to be arranged in an ordered manner. A brief discussion is given of a part likely to be played by electronic energy loss induced Coulomb explosion of target atoms for each point of fragment entry.     

Magnetic domain structures of precipitation-hardened SmCo 2：17-type sintered magnets： Heat treatment effect

The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain （so-called interaction domain） is a characteristic magnetic domain pattern of the SmCo 2：IT-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk SraCo 2：17-type sintered magnets.     

Magnetic Impurity Band and Photoinduced Magnetic Phase Transition in Diluted Magnetic Semiconductors

Applying the dynamical coherent potential approximation (dynamical CPA) to a model of diluted magnetic semiconductors (DMSs), in which both random impurity distribution and thermal fluctuation of localized spins are taken into account, the spin-polarized band and the carrier spin polarization are calculated for various magnetizations. In order to clarify the role of impurity depth on the occurrence of ferromagnetism, three typical cases are investigated: (a) II-VI DMS, (b) deep impurity level, and (c) strong exchange interaction. The present study reveals that the impurity depth of magnetic ions strongly enhances the carrier spin polarization (CSP) and accordingly, leads to a high Curie temperature. This means that photoinduced ferromagnetism with high Curie temperature can be expected in a DMS with a deep impurity depth and strong exchange interaction.     

神经节苷脂的红外、紫外光谱分析及其多聚体结构的原子力显微镜观测

神经节苷脂(gangliosides, Gls)是一类含有唾液酸的酸性鞘糖脂,是神经细胞膜的重要组成成分,在生物膜中起着非常重要的生理作用。文章用红外光谱(IR)、紫外光谱(UV)、原子力显微镜(AFM)分别对以牛脑为原料,采用Folch萃取法、硅胶吸附柱层析和DEAE-SephadexA-25离子交换柱层析得到的神经节苷脂的分子官能团和多聚体结构进行了研究。实验结果表明,从100 g湿组织中获得产品为55.2 mg,纯度达62.84%,其紫外光谱吸收在195 nm处。通过红外光谱研究证明在提纯的产品结构中含有唾液酸分子的结构片段。利用原子力显微镜对其在水中的聚集体微观形貌进行了观察研究,发现神经节苷脂在水中呈清晰的纳米级球状或椭球状结构,经测定：神经节苷脂多聚体的大小在55～380 nm之间,平均大小为(148.9±66.7) nm;高度在1.0～5.0 nm之间,平均高度为(3.25±1.01) nm。该实验结果为神经节苷脂的生物活性研究以及作为神经类药物的开发利用提供了理论和实验依据。     

Live morphological analysis of taxol-induced cytoplasmic vacuolization [corrected] in human lung adenocarcinoma cells

Taxol (paclitaxel), one of the most active cancer chemotherapeutic agents, can cause programmed cell death (PCD) and cytoplasmic vacuolization. The objective of this study was to analyze the morphological characteristics induced by taxol. Human lung adenocarcinoma (ASTC-a-1) cells were exposed to various concentration of taxol. CCK-8 was used to assay the cell viability. Atomic force microscopy (AFM), plasmid transfection and confocal fluorescence microscopy were performed to image the cells morphological change induced by taxol. Fluorescence resonance energy transfer (FRET) was used to monitor the caspase-3 activation in living cells during taxol-induced cell death. Cells treated with taxol exhibited significant swelling and cytoplasmic vacuolization which may be due to endoplasmic reticulum (ER) vacuolization. Caspase-3 was not activated during taxol-induced cytoplasmic vacuolization and cell death. These findings suggest that taxol induces caspase-3-independent cytoplasmic vacuolization, cell swelling and cell death through ER vacuolization.     

Surface fission tracks in diamond

Scanning Probe Microscope (SPM) images reveal important fingerprint features of latent tracks induced in diamond by fission fragments from a californium source. Collimated fission fragments with a binary distribution of the predominant energies of 79.4 and 103.8 MeV, are assumed. Cavities, reticular formations around these cavities, and black spots of graphite were found. A brief discussion on the possible track formation mechanism is given on the basis of the explosion spike theory; an attempt to determine latent track core and halo parameters is included.     

Magnetic properties and domain structures of FeSiB thin films

Smooth Fe₇₈Si₁₀B₁₂ thin films were prepared by r.f. sputtering with the very slow deposition rate of 0.59 nm/min. The as-deposited films were not fully amorphous, instead α-Fe(Si) nanocrystallites were found to be embedded in the amorphous matrix. The saturation magnetostriction λ_s of the as-deposited film is about 6.5 × 10⁻⁶. After annealing at 540 °C for 1 h in an ultrahigh vacuum (4.5 × 10⁻⁵ Pa), the fraction of α-Fe(Si) crystalline phase largely increased, and correspondingly the λ_s decreased to 4.5 × 10⁻⁷. Ripple domain structures were observed in the as-deposited film, while dense stripe domains were observed in the annealed sample, characterized by a very narrow domain width of 80 nm. (1 1 0) texture and island-like configuration of α-Fe(Si) nanocrystallites formed by the annealing treatment are responsible for the perpendicular anisotropy. For the as-deposited film, the magnetization curves increased linearly with the increase of the magnetic field, and showed the very small hysteresis. On the other hand, the annealed sample clearly showed a very steep jump near the origin, which is due to the switch process of the dense stripe domain.     

Magnetic moments of baryons in broken SU(4)

Assuming that the anomalous magnetic moment interaction has the formaT ₁ ¹ +bT ₂ ² +cT ₄ ⁴ +sT _α ^α in SU(4), which may arise due to symmetry breaking or some other dynamical effects, we have obtained the magnetic moments and the transition moments of the ordinary and charmed baryons.     

Magnetic correlation,excitation and slow dynamics in concentrated spin-glass alloys

Three kinds of neutron scattering experiments have been performed to clarify the role of magnetic clusters on the various properties of re-entrant spin-glasses. The presence of two kinds of spin-wave excitations, the limitations of magnetic phase diagrams and the mechanism of slow dynamics have been discussed based on the results of inelastic scattering, diffuse scattering and time-resolved small-angle scattering experiments, respectively.     

Theory for the Exciton Magnetic Polaron in Diluted Magnetic Semiconductors with Thermodynamic Fluctuations of Magnetization

The photoinduced self-trapped exciton magnetic polaron (ST-EMP) in diluted magnetic semiconductors has been the subject of intensive investigations related to the observed photoluminescence during the last two decades. The stability, however, seems still controversial. In this article we study the stability of ST-EMP theoretically, including thermodynamic fluctuations of magnetization. The calculation suggests that the EMP in CdTe(Mn) (Mn: 10-20%) is not self-trapped except at low temperatures below ¨ 1 K, but the other primary localization mechanisms, for example, alloy potential fluctuations, are necessary to the localization of EMP above ¨ 1 K.