Nanocrystalline structures offer a new opportunity for tailoring soft magnetic materials The most prominent example are devitrified glassy FeCuNbSiB alloys which reveal a homogeneous ultrafine grain structure of bcc-FeSi with grain sizes of typically 10-15 nm and random texture Owing to the small grain size the local magneto-crystalline anisotropy is randomly averaged out by exchange interaction so that there is only a small anisotropy net-effect on the magnetization process Moreover the structural phases present lead to low or vanishing saturation magnetostriction which minimizes magneto-elastic anisotropies Both the suppressed magnetocrystalline anisotropy and the low magnetostriction provide the basis for the superior soft magnetic properties comparable to those of permalloys or near zero-magnetostrictive Co-base amorphous alloys but at a higher saturation induction Like in other soft magnetic material the hysteresis loop can be tailored by uniaxial anisotropies induced by magnetic field annealing

https://iopscience.iop.org/article/10.1088/0031-8949/1993/T49A/054/pdf

Nanocrystalline soft magnetic materials

An overview of magnetostriction, its use and methods to measure these properties

Novel accurate and stable measurement methods for the magnetostriction constant lambda /sub s/ and the induced anisotropy constant K/sub u/ are presented for amorphous wires. The two constants are theoretically expressed using a magnetization rotation model with or without tensile and compressive stresses. Values of flux densities B/sub s/, B/sub r/, and B/sub m/ are estimated, observing 60 Hz BH characteristics of the amorphous wire to which a compressive stress is applied in order to realize the magnetization rotation behavior. Measured variations of lambda /sub s/ and K/sub u/ of wires of different compositions for heat treatments with or without stresses are given. A figure of merit for stress sensor constitution is proposed as lambda /sub s/B/sub s//K/sub u/, a maximum value of which is obtained due to a compressive stress anneal for Fe-rich wires. >

Magnetostriction measurements for amorphous wires

Surface crystallization and magnetic properties of Fe84.3Cu0.7Si4B8P3 soft magnetic ribbons

Trends in optimization of giant magnetoimpedance effect in amorphous and nanocrystalline materials

A new method was developed to measure the saturation magnetostriction of a thin amorphous ribbon. It is based on the use of small-angle magnetization rotation to measure the change in anisotropy field caused by the tensile stress. Measurements have been performed on Metglas 2826, 2605, and Co-Si-B amorphous ribbons. The maximum experimental error of the measurement was estimated to be about ±5 percent. It is shown that the sensitivity of the method depends on the shape anisotropy field. The estimated sensitivity was about 2 × 10-7for Metglas 2826 ribbon with 1.8 mm × 40 μm × 12 cm in dimensions.

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Measurement of saturation magnetostriction of a thin amorphous ribbon by means of small-angle magnetization rotation

Compositional effects on magnetic properties on Fe-Si-B glassy alloys

Anisotropic magnetoresistance ratio (AMR) was measured for binary and ternary (Fe,Co,Ni)‐B amorphous alloys over the temperature range from 77K to room temperature varying the composition systematically. The largest AMR at room temperature was 0.45% for (Fe0.95Co0.05)84B16 alloy, which is smaller by about one order in magnitude than those in crystalline binary transition metal alloys. It was found that AMR in Co‐Ni‐B alloys exhibits a maximum similar to crystalline Co‐Ni alloys. The maximum values were obtained for the alloys having magnetic moment of 0.56μB regardless of composition, meaning that the rigid band model is applicable to the anisotropic magnetoresistance in Co‐Ni‐B amorphous alloys.

J. Yamasaki

Papers

Measurement of saturation magnetostriction of a thin amorphous ribbon by means of small-angle magnetization rotation

Compositional effects on magnetic properties on Fe-Si-B glassy alloys

Anisotropic magnetoresistance in transition metal‐boron amorphous alloys