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

We present nonlinear magnetization measurements in the AgMn spin glass in a wide concentration range (0.4% 0.1 and H>0.1. This point of view may also help to clarify the diversity existing between the values of the critical exponents determined in other systems Mesures d'aimantation non lineaire pour les verres de spin Ag−0,4 a 24% Mn. L'analyse des resultats dans le cadre d'une transition de phase T g conduit a determiner des valeurs pour les exposants δ, γ et β a partir de trois determinations experimentales independantes dans le domaine de temperature et de champ magnetique (T−T g )/T g <0,1, ou l'aimantation lineaire est inferieure au dixieme de l'aimantation totale

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Determination of the critical exponents in the Ag Mn spin glass

Ac linear and nonlinear susceptibilities, χ0 and χ2, of ferrimagnetic FeCr2S4 single crystals were measured in the temperature range from 4.2 to 300 K for different driving ac and applied dc magnetic fields in the frequency range of 10−1–103 Hz. For high driving ac fields the real part of χ0 exhibits a cusp at around Tm≈60 K correlated with the onset of dc magnetization irreversibilities. The imaginary part of χ0 shows a strong increase below 100 K and nonmonotonic temperature dependence with a maximum shifted toward low temperatures with an increase in the driving field. Both real and imaginary parts of the linear susceptibility, χ0′ and χ0″, show a pronounced frequency dependence between 90 and 20 K with a maximal difference at around 60 K. Below the Curie temperature the real part of the nonlinear susceptibility, χ2, exhibits a broad negative peak which is strongly shifted towards low temperatures with an increase in the driving field. No clearly divergent behavior of χ2′ around Tm is observed. The fie...

P. Gaunt

Papers

Critical behavior of an amorphous ferromagnet