In LPI produced the first single crystals of the new high-temperature superconductors based on iron

In the Physics Institute. Lebedev (FIAN) synthesized a new crystal high temperature superconductor (HTS) based on iron. At the end of last year was completed laboratory equipment for solid phase synthesis and the growth of crystals of high-temperature superconductors. The result of the first experiment showed the fundamental possibility of such crystals in the LPI.


 Photo source:fian-inform.ru

Recently was exactly one hundred years since the discovery of superconductivity by Kamerlingh Onnes. In the initial period of its superconductivity carriers were mainly metals, and the maximum temperature does not exceed the critical 10K (9K in Nb, 7.2K in Pb). With further development to the 70s of the twentieth century has reached a critical temperature 23K (Nb3Ge). In the same period were obtained compound Nb-Ti and Nb3Sn, the use of which has opened up the possibility of creating high-field superconducting magnets. These materials are still made of wire, used for the manufacture of magnets, which are widely used in medicine, scientific research.

In 1986, Swiss scientists Bednorz and Müller discovered high-temperature superconductors (HTSC) based cuprates, where the superconducting transition temperature is reached 36K (Substance was previously synthesized in France and the USSR, the Institute of Inorganic Chemistry, but to the critical temperature, its resistance was not fathom). Then, the development proceeded very rapidly — within a few years the critical temperature reached 135K in compounds based on mercury, which participated in the creation of Physics of Moscow State University Antipov Putilin. After the discovery of high-temperature superconductors have been published a great number of works have been successfully used not previously used for the study of superconductivity variety of research methods of crystal structure, the electronic properties of these materials.

In 2008, the discovery of new superconductors — pnictides, where superconductivity is realized in the layers of Fe-As. In pnyctides superconducting transition temperature is high enough (55K), And their superconducting properties at relatively low (compared to other known superconductors) affected by the magnetic field. To date, the critical magnetic field of the record is marked in the pnictides. But the most surprising fact is the fact that the high-temperature superconductivity is realized in the compounds where iron (a well-known magnet) is one of the elements of the unit cell, as in the early stages of the development of superconductivity was thought that superconductivity and magnetism — two mutually exclusive phenomena. Today pnictides are considered as very promising materials for use in practice.

Says a senior researcher at the Laboratory of superconductivity LPI Candidate of Physics and Mathematics Yuri dace"Late last year, the institute has earned a laboratory for new superconducting materials. Basically we implement two methods. A simpler — a solid phase synthesis, where the initial elements in accordance with the stoichiometric formula thoroughly mixed, then sealed in the vial and baked. As a result of chemical reactions under high temperature polycrystalline compound obtained where the crystallites are randomly oriented. This is not good for the study because pnictides are anisotropic material. For this reason, an important element for the research is to obtain single crystals.
For this purpose can be used the simplest way when the substance can be simply melted and slowly cool it, or more technologically acceptable when appropriate solvent chosen, which allows to reduce the temperature of the process. This may be, for example, potassium chloride or tin metal or nonstoichiometric mixture of elements included in the crystal. The process technology is very complex, however, we were able to spend a successful experience. Obtained crystals of the compound 1-2-2 on the basis of barium with a small substitution for potassium. Although not obtained the optimum temperature (32K), But only 8K, This result is very important. Indeed, in Russia, such crystals are just beginning to grow. In the coming months, we have prepared a few more experiments — hope to reach the optimal critical temperature for this class of high-temperature superconductors. Physics researchers are waiting crystals such as ideas for research quite a few of their properties.
Also, most recently, took shape within a new fashionable now — the so-called topological insulators. This material, on the border which under certain conditions can cause persistent currents. Theorists suggested several possible types of such materials, and the first experimental studies in the world have already begun. This problem is also related to superconductivity, and — in some cases, topological insulators become superconductors. And we are now the first experiments on crystal growth of topological insulators, which can be expected to be used in the development of devices based on spintronics
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