Amorphous ribbons of composition Fe/sub 74.5-x/Cu/sub x/Nb/sub 3/Si/sub 13.5/B/sub 9/ (x=0, 1 at.%) have been annealed between about 500 degrees C and 900 degrees C. This produced a series of crystallized samples with grain sizes between about 10 nm and 300 nm and with coercivities H/sub c/ and initial permeabilities mu /sub i/ varying over several orders of magnitude. The best soft magnetic properties (H/sub c/ approximately=0.01 A/cm and mu /sub i/ approximately=80*10/sup 3/) were observed for the smallest grain sized of about 10 nm. With increasing grain size D, coercivity steeply increases following a D/sup 6/-power law (up to D approximately=50 nm). H/sub c/ then runs through a maximum of H/sub c/ approximately=30 A/cm and decreases again for grain sizes above 150 nm according to the well-known 1/D law for polycrystalline magnets. The initial permeability was found to vary in a similar manner, essentially being inversely proportional to coercivity. The variation of the soft magnetic properties with the average grain size is discussed and compared with the predictions of the random anisotropy model and other theories for the magnetization reversal. >

Grain size dependence of coercivity and permeability in nanocrystalline ferromagnets

Understanding the correlation between magnetic properties and nanostructure involves collaborative efforts between chemists, physicists, and materials scientists to study both fundamental properties and potential applications. This article introduces a classification of nanostructure morphology according to the mechanism responsible for the magnetic properties. The fundamental magnetic properties of interest and the theoretical frameworks developed to model these properties are summarized. Common chemical and physical techniques for the fabrication of magnetic nanostructures are surveyed, followed by some examples of recent investigations of magnetic systems with structure on the nanometer scale. The article concludes with a brief discussion of some promising experimental techniques in synthesis and measurements.

Magnetic Properties of Nanostructured Materials

https://www.andrew.cmu.edu/user/dl0p/laughlin/pdf/PMS.pdf

Amorphous and nanocrystalline materials for applications as soft magnets

Amorphous ribbons of composition Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 13.5/B/sub 9/ have been annealed above their crystallization temperature, which produces a homogeneous, ultrafine grain structure of alpha FeSi with typical grain diameters of 10-20 nm. The temperature dependence of saturation magnetization reveals two different magnetic phases which correspond to the alpha -FeSi grains and the grain boundary phase, respectively. The nanocrystalline material exhibits excellent soft magnetic properties which are discussed within the framework of the random anisotropy model. >

Grain structure and magnetism of nanocrystalline ferromagnets

Size effects in materials due to microstructural and dimensional constraints: a comparative review

The magnetic properties of Fe‐Si‐B‐M (M: additives) alloys prepared by annealing amorphous alloys made by the single roller method over their crystallization temperature have been investigated for development of new Fe‐based soft magnetic alloys. Excellent soft magnetic properties were obtained by adding the two elements Cu and Nb to Fe‐Si‐B alloys. It was found that these new alloys, called ‘‘FINEMET,’’ have an ultrafine grain structure composed of bcc Fe solid solution. They are suitable for many kinds of magnetic components such as saturable reactors, choke coils, and transformers, because they have superior soft magnetic properties and a high saturation flux density, and because different types of B‐H hysteresis loops are obtained by magnetic field annealing.

New Fe-based soft magnetic alloys composed of ultrafine grain structure

An Fe-base soft magnetic alloy having the composition represented by the general formula: (Fe.sub.1-a M.sub.a).sub.100-x-y-z-α-β-γ Cu.sub.x Si.sub.y B z M' 60 M".sub.β X.sub.γ wherein M is Co and/or Ni, M' is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, M" is at least one element selected from the group consisting of V, Cr, Mn, Al, elements in the platinum group, Sc, Y, rare earth elements, Au, Zn, Sn and Re, X is at least one element selected from the group consisting of C, Ge, P, Ga, Sb, In, Be and As, and a, x, y, z, α, β and γ respectively satisfy 0≦a≦0.5, 0.1≦x≦3, 0≦y≦30, 0≦z≦25, 5≦y+z≦30, 0.1≦α≦30, β≦10 and γ≦10, at least 50% of the alloy structure being fine crystalline particles having an average particle size of 1000 Å or less. This alloy has low core loss, time variation of core loss, high permeability and low magnetostriction.

Fe-base soft magnetic alloy and method of producing same

PURPOSE:To produce an Fe-base soft magnetic alloy having excellent magnetic characteristics by preparing an alloy which consists of specific ratios of Fe, Co, Ni, Cu, Si, B, Nb, etc., and in which the majority of the structure consists of fine crystal grains. CONSTITUTION:A ribbon-shaped amorphous alloy (about 5-100mu sheet thickness) is formed by a liquid rapid cooling method from the molten alloy having the compsn. expressed by (Fe1-aMa)100-x-y-z-alphaCmuxSiyBzM'alpha (where M is Co and/or Ni, M' is at least one kind of element among Nb, W, Ta, Zr, Hf, Ti, and Mo, 0 =50% of the structure consists of fine crystal grains (about <=1,000Angstrom average grain size) and which is extremely low in core loss, small in the change of the core loss with lapse of the high in magnetic permeability and saturation magnetic flux density and excellent in wear resistance is thereby obtd.

Fe-base soft magnetic alloy and its production

PURPOSE:To prepare an alloy low in core loss and high in magnetic permeability by preparing the Fe base soft magnetic alloy in which Fe content, average grain diameter, core loss and effective magnetic permeability are specified. CONSTITUTION:A ribbony amorphous alloy is formed from molten metal constituted of a compsn. shown, e.g. by the formula (M denotes Co or the like, M' denotes Nb or the like, M'' denotes V or the like and X denotes C or the like as well as 0 =60 are satisfied) by a single roll method or the like. This amorphous ribbon is worked into a prescribed shape and is subjected to heat treatment at about 450 to 700 deg.C for 5min to 24hr to prepare the Fe base magnetic alloy having >=60 atomic % Fe content and consisting essentially of fine crystalline grains of main constituting elements with =15000 and saturation magnetostriction to -1.0X10 to 6.0X10 .

Fe base soft magnetic alloy

PURPOSE: To obtain a high-hardness alloy having fine crystal grain structure by forming a molten metal having a specific compsn contg Fe, Cu, Si, B, etc, into an amorphous alloy by a liquid quick cooling method, etc, then subjecting the alloy to a heat treatment CONSTITUTION: The amorphous alloy is formed by the ordinary liquid quick cooling method such as single roll method from the molten metal having the compsn expressed by the formula or the compsn in which ≤5% of the above- mentioned compsn is substd with ≥1 kinds of elements among Mg, Ca, Sr, Ba, N, O, and S The amorphous alloy is otherwise formed by a sputtering method, vapor phase quick cooling method such as vapor deposition method or laser projection method This amorphous alloy is then subjected to the heat treatment consisting in heating and holding the same for the specified time The high-hardness alloy having the structure in which ≥50% consists of the fine crystal grains is obtd The amorphous alloy is preferably heated for about 5minW24hr at about 450W700°C in the above-mentioned heat treatment This heat treatment is preferably executed in multiple stages or plural times The alloy suitable for applications such as tools, magnetic head material and cuttlery where high hardness is demanded is obtd COPYRIGHT: (C)1988,JPO&Japio

Shigeru Oguma

Papers

New Fe-based soft magnetic alloys composed of ultrafine grain structure

Fe-base soft magnetic alloy and method of producing same

Fe-base soft magnetic alloy and its production

Fe base soft magnetic alloy

High-hardness alloy and its production