Combined time-reversal transformation in magnetic dimer clusters of coordination compounds
Закрыть
Articolul precedent
Articolul urmator
552 3
Ultima descărcare din IBN:
2024-02-24 19:43
SM ISO690:2012
GERU, Ion. Combined time-reversal transformation in magnetic dimer clusters of coordination compounds. In: Physical Methods in Coordination and Supramolecular Chemistry, 8-9 octombrie 2015, Chişinău. Chisinau, Republic of Moldova: 2015, XVIII, p. 16.
EXPORT metadate:
Google Scholar
Crossref
CERIF

DataCite
Dublin Core
Physical Methods in Coordination and Supramolecular Chemistry
XVIII, 2015
Conferința ""Physical Methods in Coordination and Supramolecular Chemistry""
Chişinău, Moldova, 8-9 octombrie 2015

Combined time-reversal transformation in magnetic dimer clusters of coordination compounds


Pag. 16-16

Geru Ion
 
Institute of Chemistry
 
Disponibil în IBN: 17 aprilie 2020


Rezumat

The coordination compounds of ions with unfilled up 3d- and 4f-shell containing dimer magnetic clusters in a weak or intermediary crystalline field are considered, taking into account that the distance between clusters is more that the distance between ions forming the clusters. In this case it is possible to neglect the exchange interaction between electrons of different clusters and the structure of ground state of separate dimer is determined by intracluster exchange, spin-orbit, magnetic dipole-dipole and hyperfine interactions. Supplementary simplification consist in neglecting effects of covalency, conditioned by overlapping of the electrons orbitals of cation and electrons of neighboring diamagnetic ions or atoms. By this we exclude from consideration complexes of 4d- and 5d-groups, as well as cyanides of 3d-groups and complexes containing ions with partially filled up 5f-shell (actinides). However, even after these restrictions the number of complex compounds satisfying above mentioned demands is sufficiently large. It is also required that for considered 3d- and 4f-shells the effects of interconfigurational interaction are sufficiently weak. In these conditions the wave function of the hole in unfilled up shell of paramagnetic ion may be obtained from the wave function of electron of the same shell with the help of antiunitary time reversal operator. Within the framework of this approach by introduction of so-called “combined time-reversal transformation” it will be shown the possibility for transformation of antiferromagnetic type of exchange interaction in dimer cluster into ferromagnetic one. Let us imagine to ourselves for an instant that under the action of time-reversal operator on the wave functions of paramagnetic ions of dimer, being in coupled state due to exchange interaction between them, the reversion of signs of the spin projections operators takes place only to one of centers, for example, to the ion with spin S1, and no changes take place to spin projections operators of the second ion (that is not true). Such a transformation will be called a ”partial time-reversal”. It is clear that under the action of the partial time-reversal operator T1 the spin Hamiltonian of the isotropic exchange interaction between paramagnetic ions of the magnetic dimer cluster H = −JS1S2 (1) does not remain invariant, but changes its sign (T1HT1-1 = - H). To restore the time-reversal invariance of the spin Hamiltonian it is necessary to perform the additional transformation (T2HT2-1 = - H). Then the time-reversal operator T can be presented in the form T = T1T2 and the time-reversal symmetry will be restored (THT-1 = H). However, it is a trivial result. If instead of T2 to introduce the operator of isomorphic substitution O2 which change in the cluster the second 3dn ion by 3d10-n ion (or the second 4fm ion by 4f14-m ion), then the time-reversal invariance of the spin Hamiltonian (1) also will be restored T1O2HO2-1T1-1 = H. (2) The analogical relationship take place if change T1 by T2 and O2 by O1. The role of operators O1 and O2 can be performed by chemist experimenter (!). The experimental data confirming actuality of the unusual definition of combined time-reversal transformation will be presented.