THE MAGNETIC PROPERTIES OF HIGHTEMPERATURE SUPERCONDUCTORS

Summary. The success of the practical use of HTS materials depends on many interrelated properties of superconductors. These properties has chemical stability. That is why the question of stabilizing the superconducting properties of HTSC compounds has a very important practical significance. The effect of substitution of Ln for the rare earth elements was analysed, it is an important element in deciding ho whether to improve technical characteristics of superconducting materials. The synthesis of samples was made in systems Er1- xAxBa2Cu3Oy (A = Pr, Tb, Ce: 0,05d”xd”0,5) by ceramic technology. In each system radiographic study of the synthesized compounds was performed, oxygen content was determined and dependence of its content on the degree of substitution of REE, which is an important element in deciding whether to improve technical characteristics of superconducting materials and further development of scientific ideas and material science. Well known that the change of oxygen content in compounds Ln123, caused by heat treatment, leads to structural phase transitions, which are closely related to changes in the electronic and magnetic properties. The increase in concentration of intercalated oxygen in intercalated basis CuO planes causes the increase of oxygen index y. Twodimensional Ising model was used to describe the process of filling CuO layers with oxygen and the formation of ordered structures in a number of works, which allowed to calculate the phase diagrams of the synthesized compounds. Well known that an increasing number of intercalated oxygen Ln123 causes to increasing concentration of free carriers (holes) in proportion to changes in oxygen index. However, a phase semiconductor-metal transition occurs on the verge of transition from tetragonal phase to rhombic and disappearance of antiferromagnetic ordering in the CuO layers. It is showing in the concentration dependences of properties such as conductivity, permittivity and magnetic susceptibility. Electrical conductivity of the samples was studied and the dependence of the superconducting properties of the type of replacement atoms was found.