Oct 23, 2020   1:38 a.m. Alojza
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prof. Ing. Roman Boča, DrSc.
Identification number: 3291
University e-mail: qbocar [at] stuba.sk
 

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Supervised theses     
     

Basic information

Basic information about a final thesis

Type of thesis:
Dissertation thesis
Thesis title:Temperature Induced Magnetic Transitions in Complexes of Transition Elements
Written by (author):
Department:
Thesis supervisor: prof. Ing. Roman Boča, DrSc.
Opponent 1:
prof. RNDr. Jozef Noga, DrSc.
Opponent 2:
doc. RNDr. Martin Orendáč, PhD.
Opponent 3:
RNDr. Ján Titiš, PhD.
Final thesis progress:
Final thesis was successfully defended.


Additional information

Additional information about the final thesis follows. Click on the language link to display the information in the desired language.

Language of final thesis:English

Slovak        English

Title of the thesis:
Temperature Induced Magnetic Transitions in Complexes of Transition Elements
Summary:
Presented Thesis focuses on the theory of electronic bi-stability called spin crossover which occurs in some coordination compounds of 3d-elements. In first chapters brief introduction to the contemporary background of spin crossover materials and theoretical models is recapitulated. Three main results are presented in the Thesis. First, the concept of molecular Ising spins is introduced which served as a working tool to formulation of a general microscopic phenomenological model for spin crossover in polynuclear compounds. The approximative solution of the model for the special case of symmetric systems is derived. The model is analysed in detail for the case of symmetric binuclear systems including the intramolecular magnetic exchange interaction and presented in the form of phase diagrams. The cooperative trapping of an excited spin state is predicted as an inherent though widely overlooked component of this class of models and the necessary conditions for its presence in symmetric binuclear compounds are formulated for the first time. In the second part, the spatio-temporal temperature evolution of the locally defined spin crossover parameters is studied using Monte Carlo Metropolis method. It is demonstrated that in the systems with significant short-range interactions the distribution of the cooperativeness depends on temperature and becomes very turbulent at the transition point. Finally, the spin crossover is discussed from the broader point of view taking into account all possible ground states of a system which arise due to the non-perfect crystal field acting on the central atom. The generalization of the widely-employed Tanabe-Sugano diagrams is shown to be an appropriate working tool in this respect. It can be summarized that the Thesis contributed to the theory of spin crossover in polynuclear systems, to the deeper understanding of the behaviour of the cooperativeness in the spin crossover solids and prepared the background for the multireference definition of the phenomenon.
Key words:
spin crossover, Ising-like model, cooperativeness, magnetic exchange interaction, Monte-Carlo simulation

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