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The micromagnetic simulation of the magnetization reversal process in a Co-rich microwire with a weak helical anisotropy under the influence of applied magnetic field and dc bias current has been carried out. It is shown that due to the influence of the magneto–elastic interaction in a wire with helical anisotropy, the change of the sign of the longitudinal magnetization component under the influence of the axial magnetic field leads to a subsequent jump of the circular magnetization component at some critical value of the applied magnetic field. This leads to a non-trivial behavior of the off-diagonal giant magneto-impedance (GMI) component of the wire as a function of applied magnetic field. The effect is confirmed experimentally for two Co-rich microwires, having significantly different amplitudes of the residual quenching stress.

The design and performance of a magnetometer based on the off-diagonal GMI effect in Co-rich glass-coated microwire are presented. The sensing element of the magnetometer is a 10-mm long piece of Co–Fe–Ni–B–Si–Mo microwire with a small pick-up coil of 85 turns wounded around the microwire. The electronics with a feedback circuit is used to register an electromotive force proportional to the external magnetic field applied along the wire axis. In the absence of the feedback current the magnetometer is capable of measuring a narrow range of magnetic fields, ±3.5 μT, in the frequency range of 0–1 kHz, the level of the equivalent magnetic noise being about 10 pT Hz−1/2 at a frequency of 300 Hz. The use of the feedback circuit increases the range of the measured magnetic fields up to ±250 μT. Photo of the giant magnetoimpedance magnetometer based on the off-diagonal GMI effect in Co-rich glass-coated microwire.

The magnetic properties of soft magnetic nanotubes with a transverse anisotropy are investigated by means of numerical simulation. The structure of isolated bamboo domain wall and its evolution under the influence of axial uniform magnetic field, as well as a circular magnetic field of a DC current is investigated. Also the stability of various bamboo domain structures (BDS) in axial and circular magnetic fields is studied. It is found that the magnetic field that saturates a nanotube in axial direction is close to the anisotropy field. On the other hand, the interval of circumferential magnetic fields where a BD5 can exist is two orders of magnitudes shorter.

The dynamics of the magnetization reversal by means of head-to-head domain-wall propagation is investigated both experimentally and theoretically for magnetic labels made from Fe-rich bistable glass-coated microwires. It is shown that the amplitudes of the electromagnetic harmonics generated by bistable Fe-rich magnetic labels of the length 1―4 cm with metallic nuclear diameter of 10―20 μm are more than 5 times larger than that of similar labels made of Co-rich microwires having high permeability and low coercive force. The electromagnetic harmonics can be detected at the distances up to 15― 20cm from the magnetic label at the signal-to-noise ratio not lower than 2.0.

It is shown that Co-rich microwires with definitely negative magnetostriction have nearly linear axial magnetization curves with a very small remanence, because they are magnetized circumferentially in the absence of an applied magnetic field. For these wires a complete set of material parameters, i.e. saturation magnetization, magnetostriction constant and characteristic amplitude of the residual quenching stress is obtained by means of careful measurement of the wire response under tensile stress to slowly varying applied magnetic field. Using the same technique we demonstrate also the existence of a longitudinally magnetized core for Co-rich wires having hysteresis loops with finite remanence. The finite remanence for these wires is explained assuming the magnetostriction coefficient to be radial dependent, so that it may change sign in a certain internal point along the wire radius. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The total magnetic charges of head to head domain walls, Q = (M z ) S, are measured for a family of amorphous glass' coated Fe-rich microwires by means of time integration of the electro-motive force signals induced in a pick-up coil wound around the wire. Here (M z ) is the average longitudinal wire magnetization and S is the cross-section of the wire metallic core. The measured values of (M z ) = 1100-1200 emu/cm 3 are close to the wire saturation magnetization. This means that Fe-rich microwires of given family are nearly uniformly magnetized in its ground state, far from the wire ends. The characteristic width of the head to head domain wall is estimated to be δ∼(40-75) d, depending on the wall velocity, where d is the metallic core diameter.

The calculations of the residual quenching stresses and magnetization curves of glass-coated Co-rich microwires are carried out to study their dependence on the material parameters characterizing the properties of metallic core and glass shell of the wire. It is shown that Co-rich microwires with strictly negative magnetostriction must have small remanence and nearly linear dependence of wire magnetization in applied magnetic field. The measured hysteresis loops for a family of Co 67 Fe 3.8 Ni 1.4 Si 14.5 B 11.6 Mo 1.7 microwires do demonstrate this behaviour. The reasons for the unusual behaviour of some Co-rich microwires showing finite remanence are discussed in the paper.

The drift mobilities of electrons (0.43 to 0.70 cm2 V−1s−1) and holes (0.24 to 0.56 cm2 V−1s−1) in thoroughly purified metal-free phthalocyanine crystals have been measured by illumination with short light pulses. The mobilities of carriers of both sign diminish with increasing temperature: μ ∽ T−n, n = 1.3 to 1.5 for holes, n = 1.5 to 1.9 for electrons. The quantum yields of holes and electrons are equal in magnitude (7 ± 6 × 10−5 at 295 °K) and increase exponentially with temperature. Probably, the generation of photocarriers is caused by thermal dissociation of singlet excitons. The difference between the energy gap and the singlet exciton energy is equal to the activation energy of quantum yield (0.19 cV). Under the giant ruby laser pulse the photocurrent in pure crystals is a linear function of light intensity, whereas in crystals containing impurities the square dependence is observed. The mechanism of charge carrier production under high light intensity is probably the singlet exciton annihilation, the rate constant being 4 × 10−15 to 8 × 10−14 cm3s−1. [Russian Text Ignored].