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Author: Roman Marianna Degree: doctor of physics and mathematics Speciality:  01.04.02 - Theoretical and mathematical physics Year: 2015 Scientific adviser: Sofia Klokişner doctor habilitat, associate professor (docent), Institute of Applied Physics of the Institution: Institute of Applied Physics of the

Status The thesis was presented on the 24 April, 2015 Approved by NCAA on the 7 July, 2015 Abstract – 1.03 Mb / in romanian

Keywords

Summary

Keywords: low-spin to high-spin transitions, mixed valence, external electric field, magnetic susceptibility, polarizability of the cluster, Mössbauer spectra.

Research field belongs to the area of molecular magnetism.

The purpose and objectives of the thesis are the development of the microscopic approach for the solution of the problem of low-spin→high spin transitions in crystals containing as structural units MnIII ions or dimeric clusters FeCo and study of efects of external electric field in magnetic and polarizability characteristics of mixed-valence CuII-CuII-CuIII clusters.

The scientific problem examined in the thesis consists in the elaboration of the microscopic theoretical approach for examination of the magnetic, spectroscopic and polarizability characteristics of the compounds with labile electronic states, which allowed to explain the experimental data and to predict a series of new effects, perspective for further application in molecular and quantum electronics.

Novelty and scientific originalityof the thesis consists in the elaboration of the microscopic approach for the solution of the spin crossover problem in crystals containing MnIII ions as structural units as well as in the explication of the observed magnetic characteristics of the [MnL2]NO3 compound. The theory of charge transfer induced spin transitions in crystals containing binuclear Fe-Co clusters is new. The calculations of the magnetic properties and Mössbauer spectra of this crystal and the elucidation of the conditions that favour the mentioned transition are original. All results which refer to the problem of electric field effects in the magnetic and polarizabilty characteristics of trinuclear mixed valence clusters are new.

Scientific significance of the thesis consistes in the elaboration of the model of the mixed valence trimeric cluster in the external electric field as well as the theory of spin transitions in MnIII compounds and crystals built of binuclear Fe–Co cyanide clusters which allow the description of the spectroscopic, magnetic and polarizability properties of the mentioned systems and prevision of a series of new and interesting effects.

The practical importance of the thesis. The obtained results are useful for elaboration of new materials with improved characteristics and interpretation of experimental results obtained in the field of molecular magnetism.

Oficial Reviewers

• Anatolie Casian
  doctor habilitat, professor
• Ion Geru
  doctor habilitat, professor, Institute of the Electronic Engineering and Nanotechnologies

Council's Members

• Petru Hadji, president
  doctor habilitat, professor, Institute of Applied Physics of the
• Mihail Macovei, secretary
  doctor habilitat, associate professor (docent)
• Andrei Palii, member
  doctor habilitat, professor, Agrarian State University of Moldova
• Elerlanj Sineavschii, member
  doctor habilitat, professor
• Florentin Paladi, member
  doctor habilitat, professor, Moldova State University
• Nicolae Enache, member
  doctor habilitat, professor, Institute of Applied Physics of the
• Alexandru Cliucanov, member
  doctor habilitat, professor, Moldova State University

 Theses