Magnetic properties of Co-based and Fe-based tape amorphous alloys.

The description of the magnetic properties of amorphous alloys and comparison of the model evaluation with experimental data have been carried out in terms of the magnetic theory of disordered systems (Biryukov's theory). The hysteresis loops for a number of amorphous metallic glasses have been investigated and it also has been shown that Biryukov's hypothesis about the weak correlation between spin and electrostatic components is true for the amorphous magnetic system that permits to interpret collectively the results of different magnetometric experiments.

High temperature magnetism and microstructure of ferromagnetic alloy Si1-x Mn x.

The results of a detailed study of magnetic properties and of the microstructure of SiMn films with a small deviation from stoichiometry are presented. The aim was to reveal the origin of the high temperature ferromagnetic ordering in such compounds. Unlike SiMn single crystals with the Curie temperature ~30 K, considered Si1-x Mn x compounds with x = 0.5 +Δx and Δx in the range of 0.01-0.02 demonstrate a ferromagnetic state above room temperature. Such a ferromagnetic state can be explained by the existence of highly defective B20 SiMn nanocrystallites. These defects are Si vacancies, which are suggested to possess magnetic moments. The nanocrystallites interact with each other through paramagnons (magnetic fluctuations) inside a weakly magnetic manganese silicide matrix giving rise to a long range ferromagnetic percolation cluster. The studied structures with a higher value of Δx ≈ 0.05 contained three different magnetic phases: (a)-the low temperature ferromagnetic phase related to SiMn; (b)-the above mentioned high temperature phase with Curie temperature in the range of 200-300 K depending on the growth history and

Motion of ferroparticles inside the polymeric matrix in magnetoactive elastomers.

Ferroelastic composites are smart materials with unique properties including large magnetodeformational effects, strong field enhancement of the elastic modulus and magnetic shape memory. On the basis of mechanical tests, direct microscopy observations and magnetic measurements we conclude that all these effects are caused by reversible motion of the magnetic particles inside the polymeric matrix in response to an applied field. The basic points of a model accounting for particle structuring in a magnetoactive elastomer under an external field are presented.