The state of art is reviewed with an emphasis on recent research results and a view to identifying areas in which further developments in materials and processing might lead to even better properties and greater application of novel technology. Basis magnetic considerations are discussed, namely, B-H loop shape, core loss, magnetic anisotropy and annealing, and magnetostriction and stress effects. Materials and applications for power frequency devices are examined, covering core loss considerations, silicon steel development, metallic glasses, and high silicon materials. High-frequency and pulse applications, magnetic recording heads, and sensor and transducer applications are also discussed. Basic research questions and future directions with respect to core loss, magnetization, and stability are examined. >

Soft magnetic materials

Magnetic amorphous alloys obtained by rapid quenching of the melt are excellent soft magnetic materials with a wide range of technological applications. They also represent a significant challenge to the scientific understanding of magnetic materials, since most of the existing theories of solids assume lattice periodicity. For these reasons, the magnetic and other properties of amorphous alloys have been very actively studied over the last decade. In recent years increasing attention has been directed to the fundamental understanding of the structural, thermal and magnetic properties of the amorphous alloys. It is not only scientifically but also technologically important to achieve such an understanding, since the amorphous alloys are, in many respects, so different from conventional crystalline magnetic materials. The author attempts to summarise recent progress in research on magnetic amorphous alloys and critically assesses the present level of understanding of this new class of magnetic materials, focusing mostly on the transition-metal-metalloid glasses. He starts with a review of early developments and a discussion on the nature of glasses and glass formation and proceeds to an extensive discussion of their atomic structure, both from the experimental and theoretical points of view.

https://iopscience.iop.org/article/10.1088/0034-4885/47/12/002/pdf

Magnetic amorphous alloys: physics and technological applications

Induced magnetic anisotropy and change of the magnetostriction by current annealing in Co-based amorphous alloys

The mechanisms producing the sensitive large Barkhausen effect and the Matteucci effect in as-prepared amorphous magnetostrictive wires are investigated using colloid technique domain observations and Sixtus-Tonks domain propagation characteristics. Theoretical analysis of the pulse height of induced voltage at the pick-up windings and between both ends of the wire are made. This analysis is compared with experimental results. The Matteucci effect was remarkably improved by twisting or twisting then annealing the as-prepared wires. Jitter-less pulse generation is realized in the latter case.

Large Barkhausen effect and Matteucci effect in amorphous magnetostrictive wires for pulse generator elements

Since their introduction over two decades ago, nanostructured soft magnetic alloys have demonstrated excellent magnetic softness and improved performance over a wide range of environmental conditions. This chapter gives an updated account of progress in alloy design, synthesis, structure, and performance of this class of alloys. Existing data are reviewed to highlight recent advances and promote new perspectives for future work in this area.

Nanocrystalline Soft Magnetic Alloys Two Decades of Progress

A new method to improve the magnetic properties of amorphous alloys by fast annealing is introduced. The zero-magnetostrictive Fe 4.7 Co 70.3 Si 15 B 10 amorphous alloy was flash-annealed by the resistive heating of short (of the order of a second) electric current pulse flowing through the sample. The heating/cooling rate was of the order of 104-105K/min. This enables the sample to be annealed at much higher temperatures (estimated 800°C) without causing crystallization, compared to the conventional annealing methods. The maximum permeability of a zeromagnetostrictive alloy obtained by this method is higher than those obtained by the conventional annealing, with the additional benefit of smaller disaccomodation effect.

Flash annealing of amorphous alloys

The disaccommodation of magnetic permeability D 3 was studied in amorphous (Fe 1-x Ni x ) 80 B 20 alloys. It was shown that the disaccommodation observed for as-quenched alloys is mostly controlled by magnetostrictive interaction and the results agree well with the theory by Allia and Vinai. However for the samples annealed in a parallel magnetic field, induced anisotropy plays an important role in the disaccommodation value, and the increase of disaccommodation as a function of Ni content is observed.

T. Jagielinski

Papers

Flash annealing of amorphous alloys

Disaccomodation of magnetic permeability at amorphous Fe-Ni-B alloys