Search

Examines the effects of thermal annealing on the frequency behavior the initial permeability of Vitrovac amorphous ribbons. Details on the experiments; Results of the study; Conclusion.

Presents a study on the effects of grain size distribution on the magnetization curve of polycrystalline ferrimagnets. Background on grain size distribution; Steps and equations necessary for the prediction of magnetization; Discussion on the Gobus model for magnetization mechanisms in polycrystalline ferrites.

A detailed study of the complex inductance response of as-cast CoFeBSi wires as a function of frequency (100 Hz–13 MHz range) and circular field amplitude [0.1–17 A/m room mean square (rms) on the surface of the wire] in the giant magnetoimpedance arrangement is presented. The analysis of experimental results show evidence of magnetization processes associated with circumferential domain walls, such as domain wall pinning, bulging, and displacement. The unpinning field was measured as 0.2 A/m (rms) at 5 kHz. It is shown that the analysis of spectroscopic plots of real and imaginary inductance leads to characterization of the magnetization process involved. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on a study which extended the domain wall size model of polycrystalline ferrimagnetics to the case of ferromagnetic amorphous ribbons. Role played by surface pinning; Assumption on the function of magnetization; Focus of the function of the domain wall size model; Mechanisms proposed to account for pinning phenomena in amorphous ribbons.

Presents information on a study which showed that the thermal dependence of the critical magnetic field can be given in terms of the saturation magnetization and the initial magnetic permeability. Experimental procedure; Results and discussion.

In this work, we present a study of the low frequency (5–13 MHz) magnetoimpedance response of amorphous microwires covered by glass. The domain wall magnetization processes active within this frequency range, namely reversible bulging of domain walls and hysteresis, are characterized through the complex inductance formalism, which allows the calculation of Cole–Cole plots. The characteristic semicircle formation of reversible bulging was observed and compared with a theoretical one based on a domain wall model for ferromagnetic wires, resulting in an excellent agreement. In addition, the wire’s magnetoimpedance response was found to be strongly dependent on the application of torsion strain as a consequence of a higher wire’s-induced anisotropy. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Circumferential magnetization of as-cast amorphous CoFeBSi wires was calculated in terms of the real component of the complex inductance and the ac applied field. Experimental plots, measured at low frequency (f=1 kHz) and under torsion strain, showed a maximum in magnetization values for a wire clockwise rotation of ∼120°, in contrast with the decreasing trend for counterclockwise rotations. In addition, the wall propagation field also exhibited a clear minimum for ∼120°, in agreement with the magnetization maximum. These results are interpreted on the basis of an helical anisotropy induced during the preparation of the samples. [ABSTRACT FROM AUTHOR]

Investigates the frequency behavior of commercial cobalt (Co)-(Vitrobac 6205) and iron (Fe)-based (Metglas 2605 SC) amorphous ribbons after a variety of thermal treatments. Experimental techniques; Experimental results and discussion.

M-type strontium hexaferrite was prepared by mechanosynthesis using high-energy ball milling. The influence of milling parameters, hematite excess and annealing temperature on magnetic properties of SrFe12O19 were investigated. Commercial iron and strontium oxides were used as starting materials. It was found that mechanical milling followed by an annealing treatment at low temperature (700°C) promotes the complete structural transformation to Sr-hexaferrite phase. For samples annealed at temperatures from 700 to 1000°C, saturation magnetization values (M s) are more sensitive to annealing temperature than coercivity values (H c). The maximum M s of 60emu/g and H c of 5.2kOe were obtained in mixtures of powders milled for 5h and subsequently annealed at 700°C. An increase in the annealing temperature produces negligible changes in magnetic saturation and coercivity. An excess of hematite as a second phase produces a slight decrease in the saturation magnetization but leads to a significant increase in coercive field, reaching 6.6kOe. [ABSTRACT FROM AUTHOR]