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Federal Research Center 
"Krasnoyarsk Science Center of the Siberian
Branch of the Russian Academy of Sciences"

 Федеральный исследовательский центр «Красноярский научный центр Сибирского отделения Российской академии наук»

Federal Research Center 
"Krasnoyarsk Science Center of the Siberian
Branch of the Russian Academy of Sciences"

Scientists synthesized metal-organic magnets with exceptional properties

2 November 2020 г.

Синтезированы металлорганические магниты c рекордными свойствами
An international team of scientists proposed a simple and effective approach to the synthesis of light magnets based on chromium and pyrazine. The resulting metal-organic magnets retain their properties at temperatures up to 242 ° C and they are not demagnetized by a sufficiently powerful external magnetic field at room temperature. The resulting material is superior in properties to all known synthetic molecular magnets and hardly differs from traditional inorganic magnets. The results of the study are published in the journal Science

It's difficult to imagine modern life without magnets. They are needed not only to decorate refrigerators with travel souvenirs. Processors and memory storage devices in computers, electric motors in household appliances - all gadgets and devices need magnets for operation. Everyone knows from the school course that a lot of metals or their derivatives have magnetic properties at room temperature. Despite their widespread and ubiquitous use, these materials have their drawbacks.

Traditional magnets are heavy, not easy and energetically expensive to produce on an industrial scale, and some of the derivatives, such as lanthanides, belong to rare elements. Therefore, scientists are looking for new methods to design magnets with desired properties from available compounds. One of the promising approaches is to create light synthetic magnets, with metal ions surrounded by organic molecules. Until now, all the obtained metal-organic magnets could not compete with the traditional ones in their ability to retain magnetic properties at room temperature and under an external magnetic field.

An international team of scientists from France, Spain, Finland, Great Britain and Denmark, with the participation of a researcher from the Krasnoyarsk Science Center of SB RAS, reported on the possibility of obtaining metal-organic magnets using specifically ordered layers of chromium ions surrounded by pyrazine molecules. The material also contains lithium and chlorine ions. The resulting compound does not lose magnetic properties at room temperature under the external magnetic field of up to 7500 oersteds, which is thousands of times higher than the strength of the Earth's magnetic field, and the compound retains its magnetization at temperatures up to 242 ° C.

The synthesis of molecular magnets is based on a very simple approach. To raise the operating temperature of such materials, scientists substitute neutral atoms attached to the metal with a group of atoms easily passing from one compound to another without changes. This makes it possible to bind paramagnetic metal ions first into films and then into bulk structures. Owing to the developed and applied experimental approaches, scientists demonstrated for the first time the possibility of binding metal ions and inexpensive organic compounds to create new molecular magnets with exceptional characteristics. Such compounds can be compared to much more expensive commercial counterparts.

The achievements resulted from the collaboration between physicists and chemists. Scientists were able to trace the change in valence, as well as structural and magnetic properties at the level of individual elements. It is noteworthy that the study used supersensitive methods based on synchrotron radiation sources, in particular, X-ray absorption polarization spectroscopy. Such approaches are necessary to observe materials, in which it is impossible to directly determine the degree of metal ion oxidation and to study magnetic properties of these ions.

“We have proposed a simple and effective synthetic approach to create a new generation of high-temperature, lightweight magnets. Such materials will be in great demand in the developing field of magnetic electronics, namely for the development of new information recording devices or magnetic sensors. From the methodological point of view, our study shows that polarized X-ray radiation can detect subtle effects in such structures. But a fundamental breakthrough is that molecular magnets are no longer a toy in the hands of scientists and can be useful for developers of modern electronics, ” says the Candidate of physical and mathematical sciences, senior researcher at the L.V. Kirensky Institute of Physics KSC SB RAS, Mikhail Platunov.