On the effect of exchange interaction on the impurity ion optical spectrum

Abstract

The method of effective Hamiltonian (EFH) is applied to the excited state (2E4A2) fine structure of Cr3+–Cr3+ fourth order pairs in ruby. Comparison with experimental data illustrates the importance of both the anisotropic and antisymmetric exchange interactions, and that part of isotropic exchange interaction, which is nondiagonal in the orbital variables. Various microscopical mechanisms responsible for terms in the effective Hamiltonian are discussed.

On the theory of magnetic anisotropic exchange interactions

“…[5] and the isotropic exchange interaction (Vex.) [4] are considered as a perturbation and can be expressed in the form Vk,. = u:, Va,(l TI) , where V ( l Tl) is the double tensor operator of rank 1 in the spin variables and transforming according to the Tl representation of the cubic group in the space variables 151 ; the sum in (4) runs over all one-electron states of both a and b ions.…”

“…More often the situation [4] occurs when the spin in the excited state differs from that in the ground state. I n this case the use of operators (1) and (2) becomes impossible.…”

Effective Hamiltonian Method in the Theory of Activated Crystals

“…The E F H method appeared to be very fruitful for energy spectrum calculations of exchange coupled ions with the orbitally degenerate states in crystals [12]. I n this case the exchange interaction operator cannot be represented in the simple form of I ( S , S,) but includes the orbital operators also.…”

Exchange interactions in polynuclear complexes

“…Exchange-coupled chromium pairs in corundum [9,17], yttrium and lanthanum aluminates [18,19] or the gallium spinel [20,21] have long been the object of particular attention for both experimental and theoretical [9,[22][23][24][25] reasons. On the one hand, chromium (III) is well known to show sharp R lines in the near infra-red region and is therefore a good candidate for observing small perturbations due to exchange interaction.…”