Specific features of exoelectronic emission in amorphous metal alloys

This paper reports on a study of the specific features of photo-and thermostimulated exoelectronic emission in amorphous metal alloys of Fe₆₄Co₂₁B₁₅ composition. The temperature dependences of the exoelectronic emission spectrum were established to adequately reflect the two-stage nature of the transition of an amorphous alloy to the crystalline state. The exoelectronic emission spectrum is sensitive to variations in the thermal treatment to which the alloy is subjected. Thermal treatment of an amorphous metal alloy gives rise to an increase in the exoelectron emission intensity. The growth in the exoelectron emission intensity was found to be the highest for alloys in the initial stage of crystallization.     

Anisotropy of losses in amorphous ribbons

The soft magnetic properties of amorphous ribbons are expected to be anistropic because of the shear deformation during the melt spinning procedure. In this paper the losses of an Fe₈₀B₁₄Si₆ amorphous ribbon were measured on stripes which were cut either parallel or perpendicular to the ribbon axis. The dependence of the losses as a function of peak induction and frequency suggests that there is an easy axis of magnetization parallel to the ribbon axis. After stress relief annealing this anisotropy is reduced. That is why this anisotropy is assumed to be due to internal stress introduced upon quenching.     

Off-diagonal magnetoimpedance in stress-annealed amorphous ribbons

The influence of creep-induced magnetic anisotropy on the off-diagonal magnetoimpedance in amorphous Co₆₇Fe₄Cr₇Si₈B₁₄ ribbon is investigated. Hard-ribbon-axis anisotropy is produced by continuous stress annealing. On applying DC bias current, the off-diagonal impedance becomes an antisymmetric function of applied field with a quasi-linear part around the zero field. Theoretical explanation of the phenomenon is based on classical electrodynamics. It is shown that the maximum on the frequency dependence of off-diagonal impedance, observed around 1 MHz, results from competition between the electromagnetic induction and the skin effect. The quasi-linear characteristic can be utilized in low-cost high-sensitive magnetic field sensors.     

High-frequency properties of thin amorphous ribbons

Magnetic energy losses have been investigated in Co-based near-zero-magnetostriction amorphous ribbons from DC to 10 MHz. Attention has been devoted to the properties of field-annealed ribbons thinned down to 5.8 μm and their behavior at high frequencies. A rationale is provided for the frequency dependence of the magnetic losses over the investigated many-decade range through analysis of the loss components. Ribbons annealed under transverse field benefit by limited irreversible domain wall activity and correspondingly reduced hysteresis and excess losses. Based on the near-linear response of the material and the permeability–energy loss relationship, the separate contributions of domain wall displacements and rotations to the magnetization process and the related dissipation effects are singled out at all frequencies. Very thin amorphous ribbons are shown to display lower loss and higher permeability (i.e. higher Snoek's product) than Mn–Zn ferrites at all frequencies.     

Specific features of the structure of semiconducting sms polycrystals in the homogeneity region

The structure and thermal properties of polycrystalline samples of samarium monosulfide have been investigated in the homogeneity region (Sm_{1 + x} S at 0 < x < 0.17). The X-ray structural parameters and porosity of the samples have been measured, and their correlation with the thermodynamic parameters of the first-order phase transition occurring in polycrystalline samarium monosulfide at temperatures in the range from 240 to 260 K in Sm_{1 + x} S has been established. It has been assumed that the measured nanopores correspond to voids between misoriented coherent X-ray scattering regions. It has been shown that the maximum of the absorbed heat energy is achieved in the case where the volume of the pore becomes comparable to the volume of the nucleus of a new phase of samarium sulfide, which is calculated from thermodynamic relationships.     

Specific features of the nuclear drip line in the region of light nuclei

The problem of the drip line in the region of the even isotopes ^4–12He, ^14–44O, and ^38–80Ca with respect to the emission of one or two neutrons is studied in the Hartree-Fock approximation by using the SLy4 and Ska effective Skyrme forces. The “stability peninsula” in the vicinity of ⁴⁰O is found.     

Influence of annealing on the magnetoimpedance effect in amorphous FeCoMoSiB ribbons

The effect of annealing by electric current passing through a sample prepared from the amorphous metallic alloy Vitrovac 6025 Z of the composition Fe₄Co₆₇Mo_1.5Si₁₆₅B₁₁ on the form of the dependence of the sample impedance on the external magnetic field is investigated. The results are explained on the basis of the concepts concerning the change in the preferred direction of the sample magnetization.     

Magnetic and Mossbauer study of amorphous Fe-Er-B ribbons

Amorphous Fe₈₀Er_xB_20-x ribbons (0Erbium sublattice has a cone spin structure and iron sublattice is probably close to collinear.     

Magnetic and magneto-optical properties of CoFeCrSiB amorphous ribbons

In this paper we investigate the surface magnetic properties of as-quenched (AQ) CoFeCrBSi ribbons prepared by planar flow casting method with using magneto-optic Kerr effect (MOKE). Measured hysteresis loops in longitudinal and transversal configurations enable us to obtain the information of ribbons surface magnetic properties. Moreover, we suggest new magneto-optic method, which is based on measurements of magneto-optical effects depending on DC current flowing through the ribbon. Experimental data of AQ ribbons are then compared with the model, which describes the influence of incidence angle on magneto-optical angles.     

Magnetization reversal in amorphous ribbons studied by neutron depolarization

The magnetization process in an amorphous ribbon with an easy axis perpendicular to its plane has been studied with the three-dimensional neutron depolarization technique. A simplified model of three layers is used, describing the magnetization distribution in the bulk and the two closure domain structures at the surface. Our analysis with this model gives direct experimental evidence that the magnetization process due to an applied magnetic field in the ribbon plane is dominantly accounted for by rotation processes of the local magnetization in the bulk. The influence of different types of closure domain structures on the magnetization distribution during the reversal process are discussed and compared with the experimental results.     

Frequency evolution of the magnetoimpedance effect in stress annealed Co-rich amorphous ribbons

Complex impedance measurements in the 1 kHz–10 MHz frequency range have been performed on CoFeSiB ribbons, subjected to different annealing treatments in order to modify their magnetic properties. The different impedance responses as a function of the applied magnetic field are explained by the magnetization processes that take place in the ribbons at different selected frequencies. In particular, an evolution from domain wall to spin rotation is observed in the 50 kHz–2 MHz frequency range, modulated by the changes introduced by the annealing treatments. PACS 75.30.Gw; 75.50.Kj; 75.60.Ch; 75.60.Nt; 81.05.Kf     

Optical and neutron domain structure studies of amorphous ribbons

The domain configuration of amorphous ribbons with positive, vanishing and negative magnetostriction constant λ_s has been investigated by means of the longitudinal magneto-optical Kerr-effect and a three-dimensional neutron depolarization analysis. The influence of an external tensile stress on the domain arrangement depends on the sign and the magnitude of the magnetostriction constant and could be measured quantitatively in the depolarization experiment. With the aid of the optical observations domain models have been established; these models were tested and completed by means of an analytic calculation of the corresponding depolarization matrix and a comparison with experimental data. Domain reorientation processes within the ribbons under an imposed tensile stress were found to agree with theoretical predictions. The nearly nonmagnetostrictive alloys shows neither stripe domains nor simple wide domains but a more complicated structure with several layers of domains.     

Magnetic properties and stress distribution in hydrogenated FeCrB amorphous ribbons

Amorphous Fe₈₅${}_{85}$B₁₅${}_{15}$ and Fe₈₀${}_{80}$Cr_4.3${}_{4.3}$B_15.7${}_{15.7}$ ribbons were hydrogenated from air side. During spontaneous ribbon dehydrogenation, the hydrogen concentration and the constant of anisotropy induced by internal stress were measured and the ribbon bending, characterized by curvature, was recorded. The results obtained indicate that internal stresses in samples under study are proportional to the hydrogen concentration, and hydrogen distribution is not homogeneous in the cross-section of sample. The hydrogen concentration is the largest in the region close to hydrogenated surface. The hydrogen release from this region is very fast and corresponds to the curvature decrease, and it can be, similar to the decrease of total hydrogen concentration, fitted by exponential function.     

Specific features of the electronic structure of fluorinated multiwalled carbon nanotubes in the near-surface region

The C 1s and F 1s X-ray photoelectron spectra of fluorinated multiwalled carbon nanotubes with different fluorine contents have been measured using the equipment of the Russian-German beamline at the BESSY storage ring by varying the energy of exciting photons. It has been established that two fluorocarbon phases in which the chemical bonding is characterized by a different electron transfer from carbon atoms to fluorine atoms are formed in the near-surface region of nanotubes with fluorine concentrations of 10–39 wt %. The content of the dominant first phase with a large electron transfer in nanotubes remains unchanged with an increase in the probing depth. This phase is identified as a bulk phase formed as a result of the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton without its destruction. The second phase with a small electron transfer is a near-surface phase, because it is predominantly located within two or three upper graphene monolayers and its contribution considerably decreases with an increase in the probing depth of fluorinated multiwalled carbon nanotubes.     

Experimental method for determining the total demagnetizing factor of thin amorphous ribbons

The basis of the method is the influence of the demagnetizing field on the maximum rate of magnetic flux change of the amorphous ribbon. The method allows to determine the demagnetizing factor of thin amorphous ribbons in a wide range of its values. With the proposed method the frequency dependence of the demagnetizing factor of amorphous ribbon with a helical magnetic anisotropy was found out.     

Impedance and magnetic properties of CoFeCrSiB amorphous ribbons near the curie point

The influence of temperature on the magnetic properties and magnetoimpedance of Co₆₄Fe₃Cr₃Si₁₅B₁₅ and Co₆₇FCr₃Si₁₅B₁₂ amorphous ribbons having different Curie points are studied. The impedance and its component are found to change greatly when the ribbons pass into the paramagnetic state. This finding can be used to determine the Curie point of ferromagnets and design high-sensitivity thermal transducers.