The stress effect on magnetic domain structure of Fe-Co amorphous alloys

The stress effect on magnetic domain structure has been studied for the Fe-Co amorphous alloy system. The domain structure was dominated by the magnetostriction-internal stress coupling. By applying the tensile stress, the domain structure was changed significantly according to the magnitude and sign of magnetostriction. The value of internal stress estimated was about 3×10⁸ dyn/cm² and nearly constant for all the alloy composition.     

On the topology of the Fermi surface in dense neutron matter

The model of dense neutron matter has been considered, where the topological rearrangement of the ground state of the system of Landau quasiparticles, which is associated with the appearance of the second sheet of the Fermi surface, occurs through two different scenarios. The rearrangement scenario depends on the relation between the wave vector q _c of critical spin-isospin fluctuations and the Fermi momentum p _F. Rearrangement at q _c < p _F occurs continuously with vanishing of the topological rigidity, whereas rearrangement at q _c > p _F occurs with the stepwise appearance of a bubble with a radius of about 0.5p _F in the filled Fermi sphere.     

Pressure-induced change of the Fermi surface topology in Al-based solid solutions

An ab initio study of the electronic structure and the Fermi surface is carried out for random Al-Si and Al-Ge solid solutions. At a 10 at. % Si content, a topological transition of the neck-formation type is revealed, which can account for the experimentally observed peculiarities of the transport properties of the Al-Si system. A similar transition is also found in the Al-Ge system, and the appearance of the anomalous transport coefficients at Ge concentrations of about 10 at. % is predicted. In addition, it is shown that the increase in the concentration of the dopants gives rise to nesting of the Fermi surface sheets (superposition of electron-hole pockets). This peculiarity of the Fermi surface can be responsible for the enhancement of the superconductivity and the instability of the crystal structure observed in the Al_1?xSi_x and Al_1?xGe_x solid solutions.     

Influence of the spin-orbital interaction on the kinetic properties of ferro- and antiferromagnetic alloys

The s-d(f) exchange model is used to estimate the influence of the spin-orbital interaction on the kinetic coefficients of binary ferro- and antiferromagnetic alloys, including the electric and thermal resistivities and the thermo-electromotive force.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 21–28, May, 1972.     

Phase transformations in disordered alloys of composition close to Fe3Pt

The phase transformations in disordered Fe₃Pt alloys with decrease in temperature are studied by x-ray structural analysis. Two simultaneous transformations are observed: an incomplete martensitic structural phase transition of the first kind and a -type intraphase (-phase) transformation. The martensitic transformation in Fe₃Pt alloy is preceded by the appearance of a singular pretransformational state in the -phase, in which the behavior of the fine-structure parameter differs from that in the initial state of this phase.Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences. Tomsk State Architectural and Building Academy. Translated from Izvestiya Vysshikh Uchebnykh Zavednii, Fizika, No. 4, pp. 83–88, April, 1994.     

Fermi surface changes in dilute alloys of magnesium in cadmium

The addition of Mg in concentrations up to 2 at.% is found to reduced the cross section of the Cd Fermi surface near the point H such that ? In A/?(c/a) is 4.8 ± 0.2 compared with the uniaxial compression result of 4.     

Fermi surface topology and the upper critical field in two-band superconductors: application to MgB2

Recent measurements of the anisotropy of the upper critical field B(c2) on MgB2 single crystals have shown a puzzling strong temperature dependence. Here, we present a calculation of the upper critical field based on a detailed modeling of band structure calculations that takes into account both the unusual Fermi surface topology and the two gap nature of the superconducting order parameter. Our results show that the strong temperature dependence of the B(c2) anisotropy can be understood as an interplay of the dominating gap on the sigma band, which possesses a small c-axis component of the Fermi velocity, with the induced superconductivity on the pi-band possessing a large c-axis component of the Fermi velocity. We provide analytic formulas for the anisotropy ratio at T=0 and T=T(c) and quantitatively predict the distortion of the vortex lattice based on our calculations.     

The influence of pH and bath composition on the properties of Fe-Co alloy film electrodeposition

Fe-Co films were electrodeposited on ITO glass substrates from the electrolytes with different molar ratio of Co²⁺/Fe²⁺ and different pH values (2.1, 2.9, 3.7, and 4.3) at 25 °C. The properties of Fe-Co alloy films depend on both Co²⁺ and Fe²⁺ concentrations in electrolyte and pH values was studied. The content of Co increases from 40% to 85% as the mole ratio of CoSO₄/FeSO₄ increasing from 0.50/0.50 to 0.90/0.10 in electrolyte and slightly decreases from 77% to 63% as the pH values increasing from 2.1 to 4.3. The X-ray diffraction analysis reveals that the structures of the films strongly depend on the Co content in the binary films. The surface morphologies of the films are influenced by the combined action of composition and phase structure. The saturation magnetization reaches a maximum value of 2974.03 emu/cm³ and coercivity reaches a minimum value of 42.72 Oe of the Fe_0.30Co_0.70. The saturation magnetization reaches a maximum values of 2974.03 emu/cm³ and coercivity reaches a minimum values of 42.72 Oe of the Fe_0.30Co_0.70 at pH = 2.9.     

Relation between magnetooptical effects and the topology of the Fermi surface of ferromagnetic metals

The anomalous magnetooptical effects in transition metals are related to the structure of the Fermi surface. The anisotropy parameters for the scattering of carriers by impurity centers is derived. The anisotropy parameter is calculated for the real and imaginary parts of the anomalous complex conductivity of iron for multiply connected, spin-down cylindrical surfaces around point H of the subband, for the single spin-down electron surface around point of the subband, and for the large spin-up hole surface around point H of the subband.Translated from Izvestiya VUZ. Fizika, No. 5, pp. 23–28, May, 1971.The author thanks professor E. I. Kondorskii.     

A positron annihilation study of the Fermi surface in concentrated α-phase CuGa alloys

High resolution positron annihilation studies upon a sequence of copper- gallium alloys have determined the variation of the important Fermi surface features with gallium concentration. The Hume-Rothery rules do not arise from contact between the Fermi surface at the [200] Brillouin zone boundary.     

Mn-Cu合金成分对去合金化法制备纳米多孔铜的影响

采用电弧熔炼制备出前驱体Mn-Cu合金,在稀盐酸溶液中自由腐蚀去合金化,制备出具有双连续结构的纳米多孔铜。研究了前驱体合金的成分对纳米多孔铜微观结构及Mn的选择性腐蚀程度的影响。结果表明：前驱体Mn-Cu合金的Cu原子分数为43%时,其去合金化受到抑制,存在明显的未完全去合金化的岛状结构;前驱体Mn-Cu合金的Cu原子分数为32%～23%时,可完全去合金化,形成平均孔径尺寸为20～100 nm,平均系带尺寸为30～80 nm,具有双连续结构的纳米多孔铜;前驱体Mn-Cu合金的Cu原子分数低至20%时,去合金化后存在大量裂纹,形成纳米颗粒聚集体。纳米多孔铜中存在少量的残余Mn,残余Mn的原子分数随着前驱体合金Mn原子分数的增高而降低。实验表明腐蚀液浓度对纳米多孔铜形貌也存在影响。     

Mn-Cu合金成分对去合金化法制备纳米多孔铜的影响

 采用电弧熔炼制备出前驱体Mn-Cu合金,在稀盐酸溶液中自由腐蚀去合金化,制备出具有双连续结构的纳米多孔铜。研究了前驱体合金的成分对纳米多孔铜微观结构及Mn的选择性腐蚀程度的影响。结果表明：前驱体Mn-Cu合金的Cu原子分数为43%时,其去合金化受到抑制,存在明显的未完全去合金化的岛状结构;前驱体Mn-Cu合金的Cu原子分数为32%～23%时,可完全去合金化,形成平均孔径尺寸为20～100 nm,平均系带尺寸为30～80 nm,具有双连续结构的纳米多孔铜;前驱体Mn-Cu合金的Cu原子分数低至20%时,去合金化后存在大量裂纹,形成纳米颗粒聚集体。纳米多孔铜中存在少量的残余Mn,残余Mn的原子分数随着前驱体合金Mn原子分数的增高而降低。实验表明腐蚀液浓度对纳米多孔铜形貌也存在影响。     

Effect of ion sputtering on the surface composition of tin-lead alloys

The surface compositions of two SnPb alloys (Sn_0.998Pb_0.002 and Sn_0.03Pb_0.97) were monitored by Auger electron spectroscopy during the relaxation that occurs after the cessation of argon ion sputtering. The data show that sputtering enriches the near surface region in Sn. It is concluded that, for this system, chemical bonding, i.e., the heat of vaporization, determines which component is enriched in the near surface region during sputtering.     

Fermi surface topology effect on interlayer magnetoresistance with in-plane magnetic field in layered multiband system: Application to FeAs-based superconductors

We propose interlayer magnetoresistance experiments which provide information about Fermi surface topology in layered multi-band systems. The interlayer magnetoresistance shows an oscillating behavior with respect to the azimuthal angle of the applied in-plane magnetic field if the Fermi surface is anisotropic. We discuss applications to LaFeAsO, a parent compound of FeAs-based superconductors. We show the results on the paramagnetic state and the antiferromagnetic state based on a mean field calculation.     

Effect of temperature on surface composition of Cu-Sn and Ag-Sn alloys; an ESCA study

Cu-Sn and Ag-Sn alloys containing 5% Sn were studied by ESCA. The heats of surface segregation of Sn obtained from equilibrium measurements of the surface composition as a function of temperature were found to be 12.0 ± 1.0 and 3.5 ± 1.0 kcal/mol for Cu-Sn and Ag-Sn alloys, respectively. These results are compared with the predictions of existing theories. Possible reasons for the difference between the experimental result and theoretical prediction are also discussed.     

Influence of antiphase domain boundaries on the formation of magnetic order in alloys

We consider the influence of boundaries between structural domains on the atomic and magnetic order in substitutional binary alloys. We calculate the variation of the composition at antiphase boundaries. We show that when the magnetic phase transition temperature of the alloy is below the Kurnakov point, the development of magnetic order at the boundaries may begin at higher temperatures than within the domains. It is then possible that the type of magnetic order at the boundaries may change (ferromagnetic into antiferromagnetic, or vice-versa) when magnetic order appears within the domains.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 13–17, August, 1991.     

Transitions in an atom moving close to the surface of a carbon nanotube

The phenomena occurring during atom channeling in a carbon nanotube have been considered. The applicability of first-order perturbation theory has been analyzed.     

The effect of particle size on the surface composition of microcrystalline alloys

Thin films a Ni?1at%Pd alloy, ranging in thickness from 10 to 100 Å were deposited onto alumina substrates by RF sputtering. The films were subsequently heat treated to produce small particles of the alloy with average sizes in the range 300 to 1000 Å. The surface composition of aggregates of small particles was determined by Auger electron spectroscopy after equilibration of the samples at 650°C. Average particle sizes were determined by analysis of photomicrographs taken by electron microscopy techniques. The results show a strong dependence of surface composition on particle size. A decrease of a factor of five in surface concentration of palladium is observed over the range of particle sizes studied. The dependence of equilibrium surface composition on particle size has been estimated by means of a mass balance model. While this model accounts qualitatively for the effects of particle size on surface composition, discrepancies between model predictions and the experimental results suggest the intervention of other phenomena, possibly related to capillarity effects.