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Magnetic Resonance for Materials Science

#2211


Investigation of New Materials for Electronics and Medicine by Magnetic Resonance Methods

Tech Area / Field

  • PHY-SSP/Solid State Physics/Physics

Status
3 Approved without Funding

Registration date
23.05.2001

Leading Institute
Russian Academy of Sciences / Institute of Radioengineering and Electronics, Russia, Moscow

Supporting institutes

  • Moscow State Geological Prospecting Academy, Russia, Moscow\nITEF (ITEP), Russia, Moscow

Collaborators

  • University of Illinois / College of Medicine at Urbana-Champaign, USA, IL, Urbana\nNorfolk State University / Center for Materials Research, USA, VA, Norfolk\nUniversity of Illinois At Urbana-Champaign / Illinois EPR Research Center, USA, IL, Urbana

Project summary

Overall goal of the project is to clear up the main physical mechanisms leading to the unusual magnetic and transport properties of a number of new materials promising for practical applications. The work include two lines.

1. Investigation of materials promising for application in solid state electronics, such as high-temperature superconductors (HTSC’s), conducting polymers, fullerides, manganites revealing the colossal magnetoresistance (CMR) effect, and activated crystals for quantum electronics.

2. Investigation of phenomena on the developed solid surface of the active carbon chars and in the solutions of paramagnetic complexes promising in biomedical applications, such as in vivo oximetry and contrast agents for magnetic-resonance imaging (MRI).

In spite of a large body of research and a lot of publications, the physical picture of the internal processes in these materials is far from clarity, thus restricting their practical applications. As a result of the proposed work, extensive information on all of these problems should be obtained, thus promoting synthesis of new materials with desired properties and their wide applications in the solid state electronics, biology and medicine.

Most attention will be concentrated on the phenomena related with electron and nuclear spin magnetism, such as magnetic resonance spectra, spin dynamics and relaxation. This is a distinguishing feature of the present project as compared with numerous studies which employ the transport and magnetostatic methods. Thus the both above-mentioned lines of investigation are combined with the common method based on the magnetic resonance. This technique enables one to get unique information at the atomic-molecular level on internal fields, structure, electron states and spin dynamics of the materials under study.

The electron paramagnetic resonance (EPR) of the free electrons and the paramagnetic centers localized in the bulk and on the solid surface will be studied first. Special attention will be paid to the spin relaxation processes – particularly, the longitudinal (spin-lattice) relaxation which yield information on the spectral density of the internal field fluctuations at the magnetic resonance frequency. Until recently, such measurements were not possible because of the extremely fast longitudinal relaxation processes typical of the strongly correlated metals, magnetic materials and superconductors. In the present project, this problem should be overcome by the use of an original modulation method with longitudinal detection which was elaborated recently in IRE RAS. This technique was already approved and enables one to obtain substantional results. Nuclear magnetic resonance (NMR), dynamic nuclear polarization (DNP), and optical techniques will also be employed.

The main specific aims and anticipated results of the work are listed below.

– Determination of the essential characteristics of the electron spin relaxation in the superconducting phase of the cuprate HTSC’s. As a result, the conclusion should be made on the symmetry of the superconduction pairing, the nature of the spin gap and microscopic phase separation.

– The study of EPR and spin relaxation in the fullerene nanotubes and some conducting polymers. The theoretical analysis of these data should yield information on the electron states and phase transitions.

– Theoretical and experimental investigations of the EPR and NMR spectra and spin relaxation in the doped rare-earth manganites and related materials with the perovskite structure. Antisipated results: development of the theory of the exchange interactions in magnetically diluted solids; the clearing up of the nature of the phase transitions, spin-spin correlations, and conductivity in the CMR manganites.

– Investigation of polymorphous electron and spin states of the local paramagnetic centers and clusters formed by the transient metal ions and the point defects in the activated crystals applicable in quantum electronics.

– Investigation of EPR, NMR, spin relaxation and the DNP effect in the aqueous suspensions of the carbon chars preparated with the use of the special technology in the Illinois University at Urbana-Champain. As a result, the mechanism of sensitivity of the chars to the oxygen content should be determined and the recommendations should be given on practical application in the in vivo oximetry.

– The study of EPR and the electron spin relaxation in the solutions of the rare-earth paramagnetic complexes. The expected results include the test of the existing theory, improvement of the action mechanism and elaboration of the recommendations concerning the synthesis of the effective contrast agents for MRI.

The partial and final reports should contain the generalized experimental data concerning the substantial parameters of the magnetic resonance spectra and spin relaxation in the materials under study as functions on temperature, concentration of paramagnetic centers, composition and the preparation technology. These data should be interpreted with the use of the existing and newly developed theoretical approaches. As a result, the practical recommendations should be presented.

The team of the participants includes 4 Doctors of Sciences, 6 Candidats of Sciences, as well as a number of young scientists and engineers. They are high-qualified scientists working over a long period in the fields of quantum electronics, magnetic resonance, high-temperature superconductivity, magnetic materials and low-dimensional systems. The Manager of the Project, Head of the Laboratory of Quantum Radiophysics, Professor V.A.Atsarkin, is an author of a monograph and more than 100 papers in scientific Journals, the Chair of the Moscow City seminar on magnetic resonance, a member of the Organizing Committees of Russian and International Conferences. The Sub-Manager (SSC RF ITEP), Head of the Laboratory of Neutron Physics, Professor F.S.Dzheparov, is an eminent physisist-theorist in the field of spin dynamics in disordered systems, an author of more than 100 scientific papers. The Sub-Manager (MSGPA), M.L.Meilman (Docent, Cand. Sci.), is a high-qualified expert on EPR and optical spectroscopy, co-author of 2 monographs and about 100 other publications. Collaboration between the participants is approved by many-years experience.

The main participants of the project were previously involved in military research. The EPR technique provides the foundation for quantum paramagnetic amplifiers (masers) which find use in the radar systems for early and distant detection, including the near space. The EPR analysis methods is employed in the geological prospecting for the uranium, titanium, and beryllium ores of military importance. Nuclear spin polarization is closely related with neutron physics and nuclear radiation technique. Surface phenomena are at the basis of the chemical catalysis which finds military applications. The present proposal allows to turn the efforts of the scientists participating in the project to the basic physical research which pursues only civilian objectives.

Especially important for the project are scientific contacts and mutual visits with the foreign collaborators: the Center for Materials Research at the Norfolk State University and the Illinois University at Urbana-Champaign (USA). An experience of fruitful collaboration with these scientific centers is already approved. The collaborators will provide samples for the investigation and discuss the results. Besides, the collaborators have in their disposal unique scientific equipment, such as the NMR and EPR spectrometers working at high magnetic fields, that is planned to share during the visits of the Russian participants to USA.


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