International audienceOne of the priority lines of development of physics of polymers and material science is the development of the principles of structure modification of polymeric materials and the study of the relation between the structure and the properties, aimed to their control. Nowadays, great attention is paid to investigation of severe plastic deformation (SPD) effect on the structure modification of polymers and polymeric composites as well as to the development of the simple shear based methods of formation of orientation order. The main difference between SPD and traditional methods of pressure shaping such as die extrusion, rolling, drawing is the ability to accumulate essential plastic deformation in the processed materials. At the same time, the billet form and size are maintained and there is a possibility of development of varied deformation routes in order to generate different forms of molecular orientation. The most widely used SPD methods applied to polymeric materials are equal-channel angular extrusion (ECAE) and its modified version, so-called equal-channel multiple angular extrusion (ECMAE). The investigations carried out in research centers of USA, Japan, China, France and Ukraine showed perspectives of the use of these methods for improvement of the set of the existing physical and mechanical properties and the formation of functional properties previously unknown. In particular, in the case of semi-crystalline polymers, SPD results in increase in rigidity and strength at conserved high level of plasticity. For polymeric composites, SPD facilitates homogeneous distribution and better dispersion of the filler particles within the polymeric matrix, orientation of transition layers and polymeric matrix etc. As a result, physical and mechanical characteristics higher of those of polymeric composites without SPD were achieved
The results of a study of the structural and magnetic properties of single-crystal samples of the diluted magnetic semiconductor Hg1−xCrxSe with different concentrations of chromium ions (0<x⩽0.07) in the temperature interval 50–300 K are reported. It is found that the boundary of the existence region of the homogeneous solid solution lies at chromium concentrations x<0.05. In samples with x⩾0.05 the sharp growth of the magnetic susceptibility in the region of the phase transition temperature is due not only to a transition to a phase similar to a spin-glass phase, which is observed in all the samples studied, but also to a ferromagnetic contribution from ferromagnetic inclusions of HgCr2Se4 and CrSe in those samples.
Results are presented from a study of the magnetic susceptibility and electron spin resonance (ESR) on Cr3+ and Mn2+ ions in a series of samples of the semimagnetic semiconductor Hg1−x−yCrxMnySe with x=0.02 and 0.01⩽y⩽0.08. The experimental results show that the structure of the ESR spectrum and the character of its shift with respect to magnetic field as the temperature changes depend on the ratio of the concentrations of chromium and manganese ions, which form two interacting substructures. The observed transition of Hg1−x−yCrxMnySe to a spin glass phase is not related to the distortion of the symmetry of the crystal lattice. The shared and distinctive properties of the systems Hg1−xCrxSe and Hg1−x−yCrxMnySe are determined.
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