Hamiltonian Heisenberg exchange

A. WEISS MOLECULAR FIELD AND HEISENBERG EXCHANGE HAMILTONIAN... [Pg.75]

Generalization of equation 89 to the many-electron system of a crystal is given by the Heisenberg exchange Hamiltonian... [Pg.80]

It was pointed out in Chapter II that the Heisenberg exchange Hamiltonian of equation 90, which can be directly related to the Weiss field parameters at T = 0°K by equation 94, is an excellent formal expression for the interactions between atomic spins (or moments) of neighboring atoms. There remains the problem of establishing the various spin-dependent mechanisms that contribute to the Jij. In general, there are two types of interaction cation- -cation and cation-anion-cation (or even cation-anion-anion-cation) interactions. [Pg.165]

The application of second-order perturbation theory to the Hiickel-Hubbard Hamiltonian for z close to one (Section 4.2) yields the freeon, antiferromagnetic, Heisenberg exchange Hamiltonian,... [Pg.15]

In this Section the ferromagnetic and the antiferromagnetic Heisenberg exchange Hamiltonians are derived from the Hiickel-Hubbard Hamiltonian in which the value of the coupling constant, z takes on values from - 1 to + 1. The M = N = 2, linear, extended Hiickel-Hubbard spectrum is plotted in Fig. 4.1. (Compare with Fig. 3.1)... [Pg.26]

By analogy to the ordinary-spin Heisenberg exchange Hamiltonian the isospin exchange Hamiltonian is... [Pg.62]

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