Ferromagnetic spin exchange

Therefore, ferromagnetic coupling is needed not only in the triplet orientation of the spins, but also in the spin-exchanging ability in the framework of a planar dication-diradical. 

In this, my third contribution, I apply freeon dynamics to problems of interest in chemistry and physics and compare with the results obtained by the spin paradigm. In particular I will apply freeon dynamics to the following "spin phenomena" i) spin exchange, ii) spin superexchange, iii) spin polarization, iii) spin density, iv) high-and low-spin states of the transition-metal ions, v) the periodic table, vi) ferromagnetism, vii) spin waves and viii) high-Tc superconductivity. 

McConnell s Heitler-London spin-exchange model between spin densities of opposite sign on radicals A and B 227 Ferromagnetic coupling in donor-acceptor salts 230 Model experiments and realization of ferromagnetic interactions 232... 

By the same procedure Campana et al. (1973) have shown the existence of a non-saturated surface sheet at a temperature as far below the ordering temperature of the bulk as 16.75 K. Surface spin-exchange scattering due to 4f-electron excitations explains this result. Bush et al. (1969) observed spin polarization, which can be due to impurities, in semiconducting ferromagnetic EuS films. They proposed this occurs because of an exchange interaction of the impurities with the 4f levels. 

The five d orbitals of a transition metal atom B are degenerate however, with more than one electron in the d manifold, the spin degeneracy is removed by the ferromagnetic direct-exchange interaction between electron spins in atomic orthogonal orbitals. Transition metal B cations usually introduce filled and/or empty d states within the gap between the anion p bands and lanthanide 5d bands, which lowers the probability that the lanthanide ion can have two valence states in a transition metal perovsldte. 

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