É. Kisdi-Koszó

Time and temperature dependence of nanocrystalline structure formation in a Finemet-type amorphous alloy

Abstract The magnetic softness and nanocrystalline structure formation of Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 Finemet alloy as a function of annealing temperature (500–600°C) and annealing time (5 s - 3 h) were investigated by means of magnetic measurements, DSC and X-ray diffractometry. Annealed at 550°C the grain size, the solute silicon content of α-Fe grains and the improvement in magnetic softness saturates as a function of time. The deterioration of the magnetic softness after annealing at 575°C is attributed to the Fe 3 Si compound which segregates from the α-Fe solid solution, giving a third intermediate peak on the well-known double-peaked DSC diagram. The crystallization products appearing after annealing at 600°C destroy the intergranular magnetic coupling and give rise to a magnetic hardening.

Magnetic after-effect in Fe-B amorphous alloys

Abstract The magnetic after-effect in amorphous Fe 100- x B x (13 ⩽ x ⩽ 24 at.%) alloys has been investigated. The important role of the ordering of boron atoms is shown. The boron atoms seem to have their maximum mobility at the eutectic concentration of the alloys.

Investigation of magnetic properties and thermal stability of Fe-TM-B metallic glasses

Abstract The influence of transition metal (TM) additives on the Curie temperature ( T c ), saturation magnetization ( M s ) and thermal stability of binary Fe-B metallic glasses was investigated. Parallel changes were found in M s and T c , showing typical group number effects. Nearly linear correlation has been observed between the initial temperature and activation energy of crystallization.

Development of the induced anisotropy by heat treatment in a magnetic field and under applied mechanical stress in amorphous Fe-B alloys

Abstract The effects of the annealing in a magnetic field or under applied mechanical stress on magnetic anisotropy of amorphous Fe100-xBx (13 ⩽ x ⩽ 23 at%) alloys has been studied. The results show the dependence of uniaxial anisotropy on boron concentration and suggest the role of boron ordering in these alloys.

Relaxation processes in Co75B25 amorphous alloy

Abstract Magnetic relaxation processes in the binary Co 75 B 25 amorphous alloy were investigated in the temperature range from 150 to 450 K. It was found that the disaccomodation of the reluctivity in this alloy did not exhibit a logarithmic time dependence above room temperature, in contrast to the amorphous alloy Fe 80 B 20 . It is found that the relaxation spectrum of Co 75 B 25 can be divided into two parts, irreversible and reversible, which characterize temperature behaviour of irreversible and reversible magnetic relaxations respectively. Different forms and peak temperatures of the individual relaxation spectra indicate their different distributions of activation parameters. The upper limit of activation energies Q = 1.1 eV of the reversible magnetic relaxation was determined by a simple method. Temperature dependences of initial susceptibility and critical field were related with different relaxation processes.

Recent Progress in the Application of Soft Magnetic Amorphous Materials: Alloys, Preparation, Devices

The soft magnetic metallic glasses have found a number of practical uses in various types of magnetic devices during the last ten years. This literature surveys deals with the present trends of applications. The following topics are reviewed progress in rapid solidification technologies and heat treatments, ageing, applications of metallic glasses in transformers, magnetic heads, magnetic shields and sensors.

Crystallization of Fe-RE-B quasi-binary glassy alloys

Abstract A small percentage of rare-earth additives in iron-boron amorphous alloys has a big stabilization effect on the amorphous state. Simultaneous magnetization and electrical resistivity measurements were made to determine the crystallization temperatures. The crystalline products after various isothermal heat treatments were identified by X-ray phase analysis in order to clarify the sequence of the appearance of the products.

Magnetic and stress annealing of Fe80T3B17 amorphous alloys

Abstract The influence of transition metal additives to eutectic Fe-B on the magnetic and stress induced anisotropy was investigated. The results are compared with the same properties of binary Fe-B amorphous alloys and treated by taking into account the chemical and physical properties of the transition metal in question.

Magnetic properties of Fe-B amorphous alloys containing rare earth additives

Abstract The influence of a few per cent rare earth additives to iron-boron amorphous alloy was investigated. Compared with binary Fe-B, changes in Curie temperature, magnetization, coercive force and amorphous-crystalline transition were observed. The role of the atomic size effect and the chemical properties of rare earth in these changes are discussed.

Influence of magnetothermal treatment on magnetomechanical coupling in Fe79Cr6.6B14.4 metallic glass

Abstract The maximum values of the magnetomechanical coupling coefficient k were found to be from 0.12 up to 0.18 for the samples quenched in a transverse magnetic field and from 0.11 to 0.17 for these quenched in a longitudinal magnetic field. After heat treatment these values increased to 0.25. The annealings were carried out from 80 to 380°C, i.e. up to the crystallization temperature, at which the magnetomechanical coupling vanished.