Cobalt exchange interactions

There has been a considerable effort in the physics and chemistry communities to use INS methods to study magnetic dynamics, which can often be described as spin waves. Measurements of spin wave dispersion curves can provide information about the interactions between atomic magnetic moments, the so-called exchange interactions. There have been comparatively few INS measurements on magnetic minerals. INS methods have been used to produce spin wave dispersion curves for hematite. Crystal field magnetic transitions in cobalt bearing cordierite, and spinel phases have also been studied by INS. ... 

The Akulov law corresponds magnetization saturation for polycrystals and nanoparticles without exchange interaction between them. In the system of exchange coupled particles the magnetization curve is described by another power low. Thus, the relation M observed in the experiment is indicative of the lack of exchange interaction between the cobalt nanoparticles. 

In [13a], a triplet-triplet exchange interaction requiring orbital overlap is the proposed quenching process. The very efficient quenching observed in [13c] occurs via formation of a charge transfer Intermediate, in which the zinc moiety is reduced by the cobalt system. The lifetime of this intermediate is estimated to... 

It has been concluded from a study of the optical and e.p.r. spectra of Co —Cu bovine superoxide dismutase, in which zinc has been replaced by cobalt, that the cobalt site reactivity should be described in terms of reaction of the Co-imidazolate-Cu system as a whole the crystal structure reported last year indicated that the metals were linked by a common histidine residue. There is an exchange interaction between the cobalt and copper however, this is abolished when the linking imidazole is protonated. Further evidence for the close proximity and interactive dependence of the zinc and copper binding sites was obtained from a study of the 4 Cu protein a two-fold enhancement of the activity of 2 Cu dismutase was observed upon occupation of the zinc sites by the Cu ". On the basis of C1 n.m.r. studies, Fee and Ward have suggested that one co-ordination position of Cu in superoxide dismutase is normally occupied by water they further suggest that superoxide can displace the solvent to form a cupric peroxide complex. 

The Co-exchanged zeolites were not effective catalysts for the oxidation of cyclohexane. The cobalt exchanged ions were not stabilized enough by the zeolite interactions and part of these cations were released in the oxidation medium. Thus, we decided to explore the activity of P-zeolites in which cobalt ions were incorporated into the framework. We hoped that the incorporation would increase the stability of the cation within the solid. We studied the catalytic activities of cobalt substituted P-zeolites containing aluminium (Co-Al-BEA) and boron (Co-B-BEA) towards the oxidation of cyclohexane into adipic acid. 

M. Clemente-Juan, M. Aebersold, H. U. Giidel, E. Coronado, H. Biittner, G. Kearly, J. Melero and R. Burriel Magnetic Excitations in Polyoxometalate Clusters Observed by Inelastic Neutron-Scattering-Evidence for Anisotropic Ferromagnetic Exchange Interactions in the Tetrameric Cobalt(II) Cluster [Co- 4(H20)2(PWi 034)2]" - Comparison with the Magnetic and Specific- Heat Properties J. Am. Chem. Soc. 121 10028(1999). 

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