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Notes: The magnetic anisotropy, Kσ, induced by heating under applied tensile stress has been studied for the Fe73.5Cu1Nb3Si13.5B9 amorphous alloy as a function of the annealing temperature. The induction process was carried out by means of current annealing in samples as-quenched and preannealed (TP.A.=400 °C during 2 min). It is found that the easy axis of this anisotropy is transverse to the tensile stress. The dependence of the stress induced anisotropy on annealing temperature is, in both cases, similar to that reported in other different metallic glasses when annealing at temperature below Tc=350 °C, while Kσ is practically constant (≈500 J m−3) in the annealing temperature range from 350 to 525 °C. On the other hand, the magnetostriction constant, λs, was determined as a function of the measuring temperature within the range from 4.2 K up to 600 K. The results can be well accounted for by the single-ion model up to 350 K, while above this temperature the contribution of two-ion mechnism is also inferred.

Notes: The influence of the tensile stress on the flux reversal phenomena in as-quenched state of Fe77.5Si7.5B15 is investigated. A large and stable Barkhausen jump is observed at a field H*, called the switching field. The switching field H* passes through a minimum as tensile stress increases and the jump in magnetization M* at H* grows with stress. It is observed that H* of the sample can be modified by flash annealing under stress. The results on magnetic properties like coercive field, squareness ratio, power loss of as-quenched and stress-annealed samples are presented. The stress annealing induces elastic and plastic components in anisotropy.

Notes: Measurement of the magnetostriction constant of amorphous wire by conventional techniques is very difficult because of its small diameter. However, accurate determination of the magnetostriction constant is important in the study of amorphous wires. Here the saturation magnetostriction constant (λs) for a low-magnetostriction amorphous wire of nominal composition (Fe6.3Co92.7Nb1)77.5Si7.5B15 has been determined by means of the small-angle magnetization-rotation method. λs has been evaluated to be 2.1×10−7 for its as-received state. The dependence of thermal treatment is also reported.

Notes: Idealized giant Barkhausen (BG) jumps in amorphous wires result in a simple rectangular hysteresis loop. There is a range of domain wall depinning fields so that if the depinning field for magnetization in the central section of the wire is high enough, magnetization reversal takes place by domains becoming depinned at the end of the wire. This leads to the rectangular hysteresis loop characteristic of GB. We have observed a different kind of Barkhausen effect in Fe-B-Si amorphous wires under a variety of conditions. The magnetization starts linearly with field, then displays a roughly quadratic field dependence, saturating at lower fields than that given by the low field linear extrapolation. In the quadratic region the plot of log(Hs−H) vs log(Ms−M), where Hs is the apparent saturation magnetization taking place at field Hs, is linear with a slope of 1/2. This is typical of simple second order instability processes. Thus, instead of a first order giant Barkhausen jump we have observed a second order Barkhausen process that is continuous. The only jump that occurs is in demagnetizing. This is caused by hysteresis. We believe this is the first time that this second order process has been described. From the details of the measurement we believe that the magnetization takes place by a longitudinal wall moving radially rather than a radial wall moving longitudinally as in the GB. The circumstances under which this takes place are in well-annealed wires magnetized with an imposed twist and longitudinal stress. In as-cast wires we imposed a curvature by bending along the longitudinal axis. The solenoid of the exciting field is bent the same way. The magnetization in wires with the imposed curvature displays a GB behavior for high and low curvatures. In an intermediate regime of curvature a behavior midway between GB and our second order effect is displayed. The low field magnetization looks like the second order effect but has a small jump to apparent saturation in the quadratic region described above. In summary we have found a range of depinning fields that lead to different magnetization processes when the depinning field values are less than that for central magnetization.

Notes: The dependence of the magnetic parameters as switching field H*, coercive field Hc and reduced remanence mr, on applied tensile stress σa has been studied in current annealed amorphous wires. The switching field increases as σ 1/2a in fully relaxed samples, while in both "as-quenched'' and partially relaxed samples the σ 1/2a law holds only at high values of σa. The coercive field increases with σa in a way similar to H* and mr increases up to the saturation value. This behavior can be explained by taking into account the different magnetic regions that have been proposed for these wires.

Notes: Amorphous wires are prepared by the in-water quenching technique. This procedure gives rise to local magnetoelastic anisotropies arising from the coupling between frozen-in internal stresses and magnetostriction. Azimuthal and axial components of internal stresses have been experimentally confirmed by the asymmetry of the Matteucci effect at different applied torques for the Fe77.5Si7.5B15 amorphous wire. According to classical theory of elasticity, internal stresses produced by the thermal gradient inside the wire during the quenching have been calculated. The nonzero values of azimuthal and axial stresses have been derived in addition to the well accepted radial stresses. This explains the present experimental results. Remanence and its dependence on tensile and torsional stresses has been also calculated.

Notes: The specific magnetic moment, coercive force, anisotropy field, and saturation magnetostriction constant have been measured in Co1−xPx amorphous ribbons with 0.04≤x≤0.27. Differential scanning calorimetry, x-ray diffraction, and transmission electron microscopy analysis have been made in order to study the transition from the amorphous state to the crystalline one. Results suggest that transition takes place when x decreases from 0.19.

Notes: The study of the variation of the electrical resistivity ρ between 10 and 1000 K has been performed in the Co75Si25−xBx and Co100−x(Si0.6B0.4)x ferromagnetic amorphous series. A general analysis of the curves gives useful data about the main features of ρ in these materials: Curie temperatures Tc, temperatures of the minima Tmin, crystallization temperatures Tx, temperature coefficient of resistivity, and absolute resistivity. The correlations between these magnitudes have been discussed including direct comparison with the nonmagnetic Ni-Si-B similar compounds. An analysis of the structural and magnetic contributions to the resistivity is presented in the whole temperature range. The structural part is interpreted in the framework of the extended Ziman model and it is superposed on the magnetic term. A T2 magnetic contribution coming from the spin wave scattering is found at temperatures between Tmin and approximately 0.5 Tc. At higher temperatures, the magnetic part seems to be understood taking into account the mean field approximation. Saturation magnetization M(T) measurements over 300 K were carried out in order to get an experimental hint of the correlation between the magnetic ρ and M(T) with rather satisfactory results. Besides the general analysis we report the achievement of a progressive shift of Tmin in some compounds (in particular in Co70Si18B12) in which a tentative explanation might be based on phonon ineffectiveness arguments.

Notes: The domain patterns of as-cast Fe-rich amorphous wires with 125 μm in diameter and a length of 10 cm have been observed by means of magneto-optical Kerr effect. Particular attention is paid to the observation of domains at the end and inside the wire after adequate polishing procedures. Four distinguishable regions within the wire namely, the shell, the core with diameter between 60 to 80 μm, and two different closure domain structures at the end of the wire depending on the two different remanent states, are observed. Investigating one end of the wire, we found conical-like domains with increasing diameter reaching at least several hundred μm into the wire in one remanent state, in the other remanent state we find a very small conical-like domain with decreasing diameter reaching only several ten μm into the wire. In addition, reversed domain patches inside the core up to a distance of about 3 cm from both ends can be observed. These results give a hint to enlighten the origin of the switching mechanism and its recently found alternating directional propagation.

Notes: CoSiB and FeB single layers and CoSiB/FeB bilayers with thicknesses ranging from 250 to 1500 Å were grown on bowed glass substrates using rf sputtering. A magnetoelastic anisotropy was induced in the magnetic layers after removing the films from the sputtering chamber. The positive (FeB) and the negative (CoSiB) magnetostrictive single layers showed an easy magnetization axis transverse and parallel to the compression axis, respectively. The magnetic behavior of the CoSiB/FeB bilayers is shown to be extremely sensitive to the thickness of each layer, to their thickness ratios, and also to the deposition sequence of the layers on the substrate. These results are discussed in terms of the interactions between two magnetic phases with easy magnetization axes transverse to each other. © 1999 American Institute of Physics.