Fractographic analysis of Co- and Fe-based high strength soft magnetic materials showed the high localization of the plastic deformation and the ductility in narrow shear bands. The estimated fracture toughness of these materials is closely associated with the scale of the local plastic zone.

Milling up to 800 h causes amorphous Co70.3Fe4.7Si10B15 alloy, prepared in the form of thin ribbon, to partially crystallize thus forming a powder material consisting of an amorphous phase and fcc-Co nanocrystals with an average grain size of about 10 nm. A gradual increase of the nanocrystalline fcc-Co fraction, produced by ball milling, was detected. Prolonged milling results in destabilization of the fcc-Co phase and oxidation of the powder material (presence of CoO phase after 1500 h of milling). The thermal stability studies of as-quenched and milled Co70.3Fe4.7Si10B15 alloy emphasized a two step crystallization behavior. During the first crystallization event, cobalt rich phases, i.e., fcc-Co and hcp-Co crystallize, whereas after the second crystallization event, Co2B and Co2Si are formed.

The aim of this work was to prepare powder samples of FeNi by long-time milling of microcrystalline ribbon Fe 19 Ni 81 (sample A) and that of pure elements Fe and Ni (sample B) in low-energy vibratory mill for 1000 h and to investigate their magnetic properties. We found that the coercivity of sample A and sample B steeply increases up to 140 h of milling time and then slowly increases for sample A and decreases for sample B. The magnetic moment of both samples monotonously decreases during the milling. The sample A is solid solution Fe 19 Ni 81 and its structure is stable during the milling. New phases with different Curie temperatures are found in sample B during the milling.

Nanocrystalline FeSi alloys have been prepared using the mechanical milling method (ball milling) up to 800 hours. We investigated the structure and magnetic properties of FeSi (with 6.5 wt.% of silicon) alloy. The magnetization of the sample decreases with milling time due to the decrease of powder grain size and of the increase of the fraction of paramagnetic phase.

We have investigated the structure (by TEM and SEM) and basic surface and bulk magnetic properties (by measurement of surface and bulk hysteresis loop and domain structure observations) of a Fe-Cu-Nb-Si-B/Fe-Nb-Si-B bilayer prepared by melt spinning method. We have detected perfect bonding between the two layers of the bilayered ribbon. This bonding produces tangential stress, which influences magnetic properties measured in surface layers at both sides of the ribbon.

In this paper we describe the influence of the composition and the annealing treatment on the domain structure of Fe–Si–Cu–Nb–B–Al alloys with different Al/Si content. Our observations were compared with the bulk and surface layer coercivity. We have found that aluminium influences magnetic properties and the domain structure of these alloys. Since the crystallization temperature of these alloys decreases with increasing Al content, our samples did not show any improvement of soft magnetic properties as compared with Finemet.

The low-temperature magnetization of amorphous and nanocrystalline Fe76.5−xUxCu1Si13.5B9 alloys (x = 0–11) has been studied in the 4.2–300 K range. All examined magnetic parameters (exchange integral J, range of exchange interactions 〈r2〉, magnetic moment per Fe atom, μFe, spin wave stiffness constant D) are markedly influenced by the uranium substitution for iron. Both the μFe and D are found to increase with decreasing Fe content in amorphous alloys for x = 0 up to about 4. The noncollinear spin structures as a result of competing interactions are supposed to explain this behaviour. Some samples (with U contents of 2–6 at%) annealed for 1 h at 813 K appear to be nanocrystalline. Uranium seems to inhibit grain growth in the investigated FeUCuSiB system, just as Nb does in FeNbCuSiB nanocrystalline alloys.

Temperature dependence of the magnetization in the range 4.2-300 K for Fe74-xCrxNb3Cu1Si13B9 was measured and some magnetic characteristics were calculated. The asymptotic behaviour of M(H) curves at low fields was examined. The region of onset of ferromagnetism is expected for x < 17.

The influence of uranium content and annealing on the magnetic properties and Hall effect of Fe73.5Cu1Nb3−xUxSi13.5B9 (x = 1, 2, 3) nanocrystalline alloys prepared by melt spinning were investigated. Measurements of magnetic properties of surface layers confirmed higher concentration of uranium in the air-side surface layers than in the wheel-side layers.

The low-temperature magnetization behaviour of ferromagnetic Fe73.5Nb3−xUxCu1Si13.5B9 (x = 0, 1, 2, 3) and Fe73.5U4Si13.5B9 alloys in the amorphous and partially crystallized states was studied. The experimental data can be explained by means of the usual spin wave model. The spin wave stiffness constant D, the range of the exchange interaction 〈r2〉, the exchange constant A and the magnetic moment per Fe atom μFe were determined. We have found that all these parameters are strongly affected by the substitution of Nb and Cu by U atoms.

The influence of boron content and annealing on the Hall effect and structure of amorphous Fe73.5Cu1Nb3Si22.5−xBx (5≤x≤13) ribbons were studied. The annealing at 550°C caused a significant change of structure and Hall coefficient of samples vs. boron content. DSC confirmed the influence of boron content on crystallization temperature of all samples.

The aim of this work was to study the structure dependence of the magnetic properties of Co/sub 100-x/Ni/sub x/ (x=20, 40, 50, 60) microcrystalline thin films prepared by the flash-evaporation technique. The grain size of the microcrystalline phase depends on the concentration of Ni. The domain structure which was studied by Lorentz transmission electron microscopy (LTEM) depends on the size of microcrystals and its character corresponds to that of the thin films which are suitable for longitudinal recording. The influence of annealing on the structure and the magnetic properties was studied. The annealing at temperatures above 350/spl deg/C transformed the microcrystalline structure of the films into a polycrystalline one. The grain size increased with annealing temperature and decreased with the concentration of Ni. The domain structure of annealed films has been influenced by the structural changes. After annealing at 550/spl deg/C, in addition to the ripple structure, the black and white dots (BWD) type of domain structure typical for perpendicular recording media, was observed. Experimental results obtained by TEM and LTEM were completed by the Hall effect measurements and with temperature and concentration dependencies of saturated magnetic polarization B/sub S/ and the Hall coefficient R/sub 1/.< >

The aim of this work was to study the structure dependence of the magnetic properties of Co100-xNix (x = 20, 40, 50, 60) microcrystalline thin films prepared by the flash-evaporation technique. The grain size of the microcrystalline phase depends on the concentration of Ni. The domain structure which was studied by Lorentz transmission electron microscopy (LTEM) depends on the size of microcrystals and its character corresponds to that of the thin films which are suitable for longitudinal recording. The influence of annealing on the structure and the magnetic properties was studied. The annealing at temperatures above 350-degrees-C transformed the microcrystalline structure of the films into a polycrystalline one. The grain size increased with annealing temperature and decreased with the concentration or Ni. The domain structure of annealed films has been influenced by the structural changes. After annealing at 550-degrees-C, in addition to the ripple structure, the black and white dots (BWD) type of domain structure typical for perpendicular recording media, was observed. Experimental results obtained by TEM and LTEM were completed by the Hall effect measurements and with temperature and concentration dependencies of saturated magnetic polarization B(s) and the Hall coefficient R1.

The crystallization behaviour of amorphous Fe73.5Cu1M3Si13.5B9 (M = Nb, Mo, W, Zr) alloys has been investigated by different techniques. The composition was confirmed by EDAX. Melt spun ribbons were annealed at temperatures from 300 to 700-degrees-C in vacuum 5 x 10(-4) Pa. Annealing conditions were determined with the aid of the temperature-resistivity curves. Mossbauer spectroscopy confirmed the coexistence of the nanocrystalline Fe3Si and the boron-rich amorphous phases, the content of the latter diminishing at increasing annealing temperature. The phase analyses were supported by X-ray diffraction measurements.

The changes in the hyperfine parameters of rapidly quenched amorphous Fe90−xCoxZr10 (x = 0, 5, 10) ribbons induced by hydrogenation have been studied by 57Fe Mössbauer spectroscopy. Differences in spectra of uncharged and hydrogenated samples were observed at various temperatures. The increase of the magnetic transition temperature of these alloys due to hydrogenation was observed and the influence of the substitution of Fe-atoms by Co-atoms is discussed.

Low field magnetic susceptibility of a glassy semiconductor (Sb2S3)x(SbI3)yFez reveals a spin glass-like behaviour in spite of the sample not being metallic. The critical temperature is observed to depend on the concentration of the iron atoms (TM = 0.179z0.76).

The influence of stress on components of the complex permeability of grain oriented transformer sheets has been investigated. Results show the best quality factor Q = μ′μ″ may be attained at optimal tensile stress. From this point of view, and with respect to magnetostriction, a suitable surface coating on sheets must be chosen.

The ac magnetic susceptibility of non-stoichiometric UFe2 Laves compounds was measured between 40 and 200 K. It was found that the transition temperature of the investigated compounds is directly proportional to the iron content.