Heisenberg-type exchange

The general conclusion which we can draw is that exchange forces in Tb pnictides are very anisotropic, in spite of the fact that the observed magnetization axes correspond to the predictions of the crystal-field theory. These predictions are, as is stated clearly by Trammell (1963), valid only for isotropic Heisenberg-type exchange. 

Further experiments were done on the system CeSb-CeTe by Bartholin et al. (1985), Ravot and Achard (1982), Rossat-Mignod et al. (1982a, b), Escome et al. (1984) and Ravot et al. (1983). A 5% tellurium addition converts the highly anisotropic exchange observed in CeSb into the simple isotropic Heisenberg-type exchange. Sera et al. (1985) found in the system CeBi-CeTe a transition to spin-glass behaviour. 

The interactions are of the ferromagnetic-Heisenberg type with 1% XY-square anisotropy arising from both anisotropic exchange and dipole-dipole interactions99. The xOz plane is the easy one and the spins are weakly bound in the Ox direction80,". ... 

Although there may not be a consensus on the exact mechanism of the R-T exchange interactions, it is common usage to express this interaction as an effective exchange of the Heisenberg type ... 

WIGNER FORCE. Short-range nuclear force of noncxchangc type postulated phenomenologically as pait of the interaction between nucleons. Postulated exchange forces are Bartlett, Heisenberg, and Majorana forces. 

Then Gamow talked about the Origin of 7-Rays and the Nuclear Levels and Heisenberg, on The Structure of the Nucleus, discussed the exchange forces of the two types that Heisenberg50 himself and Majorana51 had proposed not long before. 

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. 

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