Abstract
This article addresses the question of the possibility of obtaining high-spin chains and crowns of magnetic units s = 1 from doped (by a hole) antiferromagnetic architectures. It aims at determining the range of values of the double-exchange model interactions for which these molecules exhibit a high-spin ground state. Several chains and crowns of sizes varying between three to seven magnetic sites have been studied using a refined double-exchange model. It is shown that, for physical values of the parameters, linear chains of three, four and five sites are likely to adopt the highest spin state. For chains of six sites, small values of magnetic couplings are needed to get the highest spin, but it would be easy to get an S = 3/2 ground state. For systems of seven (or slightly more) sites, the highest spin state becomes non accessible but S = 5/2 states are likely to be obtained. Surprisingly, the physics of crowns is substantially different. The same trends are observed for even-number systems but with a larger double-exchange regime. At variance, odd-number systems do not exhibit a double-exchange mechanism for low values of the magnetic couplings. These observations are rationalized from an analysis of the computed spectra and wave functions.
Highlights
Magnetic systems are increasingly important in our daily life
Among the first attempts following this strategy, ferromagnetic interactions could be imposed in a series of Gd(III)Cu(II) complexes, leading to a spin S = 9/2 for instance in a complex of Gd(II)Cu(II)2 [1,2,3]
The invoked reason for this ferromagnetic interaction is the delocalization of the copper unpaired electron into the unoccupied
Summary
Magnetic systems are increasingly important in our daily life. They may be found in data storage devices, energy storage, medical imaging, etc. This can be achieved using the Ovchinnikov’s rule [16], proposed by Klein [17], which enables one to predict the spin ground state multiplicity of any alternant hydrocarbons from topological arguments This strategy, firstly exploited by several groups [18,19,20,21], is still used to conceive magnetic compounds and 2D materials with ferro-, ferri- and antiferromagnetic properties [22,23,24,25]. The double-exchange mechanism rationalizes the appearance of a high-spin ground state in mixed valence systems with several unpaired electrons per magnetic unit. For some peculiar values of the interactions between the metal ions, a double-exchange regime can be achieved leading to a high-spin ground state in doped metallacrowns. The most important results are summarized in the conclusion section where some perspectives will be discussed
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