Нанорозмірна фізика
EPR spectra of D4h Symmetry Four-Nuclear Molecular Complex
Zhuravlev A. V.
Donetsk Institute for Physics and Engineering named after O.O. Galkin
of the NAS of Ukraine, Prospect Nauki, 46, Kyiv-03039, Ukraine.
E-mail: alexander.zhuravlev01@gmail.com

A polynuclear transition metal based complex which is embedded in a diamagnetic ligand matrix magnetic metal core shall be represented as a system consist of N interacting spins which are magnetically isolated from the environment. The spin tetramers are defined as the complexes with N=4.
The spin Hamiltonian formalism has been applied to the detail description of the energy spectra and spin states of D4h symmetry four-nuclear molecular complex or the spin tetramer [1]. The evolution of the energy levels of the tetramer has been explored as a function of the local parameters of the spin Hamiltonian considering the symmetry of the complex.
In the past decade, there were synthesized and experimentally researched a number of spin s=1/2 Cu(II) tetramers mostly with EPR study [2-4]. The presented [1] model will be attached to EPR spectra treatment, so it is possible to compare directly a theory and an experiment [2-4].
Analysis of the spin-spin interactions dependences of the EPR frequency provides with the relevant parameters of the spin Hamiltonian, in particular the Dzialoshynskii–Moria interaction as well as the axial and azimuthal exchange anisotropy strengths. The exchange splitting parameter is not usually directly attainable, but can be estimated through the spin mixing mechanism.

1.	Zhuravlev A. V. Local Exchange Anisotropy Effects in D4h Symmetry Four-Nuclear Molecular Complex // Low Temp. Phys.-2015.-41.-P. 186-192.
2.	Mandal T. N., Roy S., Konar S., Jana A., Ray S., Das K., et. al. Self assembled tetranuclear Cu4(II), Ni4(II)[2  2] square grids and a dicopper (II) complex of heterocycle based polytopic ligands – Magnetic studies // Dalton Trans.-2011.-40.-P. 11866.
3.	Shuvaev K. V., Sproules S., Rautiainen J. M., McInnes E. J. L., Collison D., Ansona C. E. and Powell A. K. A self-assembled Cu(II)4 [2 × 2] grid with organic radicals // Dalton Trans.-2013.-42. 2371.
4.	Bietsch W., Mirea A., Kamleiter T., Weiss M., Schubert U. S., Weidl C. H., et. al. Exchange interaction and Jahn-Teller correlations in novel tetranuclear supramolecular Cu(II) grid // Molecular physics.-2002.-100.-P. 1957-1968.