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

Basic physics and current technologies of magneto-optical recording are reviewed. The development owes much to the discovery of amorphous rare earth-transition metal (RE-TM) films, which exhibit quite uniform magnetic and optical properties in the scale of practical interest. The RE-TM films also exhibit a wide variety of thermomagnetic properties on adjusting their composition, which resulted in the recent development of high-density recording using multilayer films. In amorphous RE-TM films it is possible to record thermomagnetically marks some several tens of nanometres in size. In order to readout such small recorded marks, further development of new readout techniques is necessary.

https://iopscience.iop.org/article/10.1088/0022-3727/34/17/201/pdf

Magneto-optical recording

The temperature dependence of the AC susceptibility Fe-rich Fe-Zr amorphous alloys having mictomagnetic or spin-glasslike behaviour has been measured in a superposed DC field. The Fe-Zr amorphous alloys containing more than 8.6 at.% Zr clearly show sharp peaks at the Curie temperature TC and the spin cluster freezing temperature Tsf. These two temperatures seem to coincide at a critical concentration for the Fe-7.6 at.% Zr alloy, which is considered to be the percolation limit for the long-range ferromagnetic interactions.

http://iopscience.iop.org/article/10.1088/0305-4608/16/7/018/pdf

Mictomagnetism of Fe-rich Fe-Zr amorphous alloys studied by AC susceptibility in a superposed DC field

The Fe−Zr (Iron-Zirconium) system

Melt spun and sputtered amorphous alloys from the a FexM100−x series with M=Y or Zr can be electrolytically hydrogenated up to a maximum of about 3 hydrogens per M, while retaining their mechanical integrity. Hydrogen uptake has been monitored in situ during hydrogenation by following the increase in length of the melt‐spun ribbons. Values of up to 7% have been found, and the corresponding increase in volume per absorbed hydrogen is approximately 0.5 A3. Hydrogen diffusion constants have been estimated from the mechanical relaxation, and activation energies of order 0.4 eV have been deduced. The binding energy is about 1 eV per hydrogen. Desorption at elevated temperatures preceeds crystallization of the alloys studied, and the hydrogen‐loaded materials retain much of their charge at room temperature for periods of order one year. Iron‐rich yttrium alloys have a moment close to 2 μB/Fe, but they are asperomagnets, the iron moments freezing in a random noncollinear arrangement which possesses a net moment,...

Influence of hydrogen on the magnetic properties of iron‐rich metallic glasses (invited)

Several kinds of Fe‐Zr amorphous ribbons have been prepared from the melt in an argon atmosphere, and the spin‐glass‐like behaviors have been investigated. The thermomagnetic history has been observed, and the freezing temperature monotonously decreases, in contrast to the Curie temperature, which increases and then goes through a maximum with increasing Zr content. Asymmetric hysteresis loops and the relaxation of remanence have also been found. The coercive force of Fe92Zr8 amorphous alloy drastically increases below 30 K, and the high‐field susceptibility of the present alloys are extremely large. These behaviors are explained in terms of the coexistence of ferromagnetic and antiferromagnetic states.

H. Hiroyoshi

Papers

Ferromagnetic‐spin glass transition in Fe‐Zr amorphous alloy system