The detailed analysis of the spin-spin hamiltonian is given. The usually used expression is shown to be incorrect, as the two-particle Breit hamiltonian, because it gives non-zero divergency of the magnetic field. The correct form of the spin-spin interaction hamiltonian is obtained, and the spin system energy in exterior magnetic field is calculated on the basis of this form. As a result the density of spin-spin interaction energy is appeared to be four times more in comparison with previous results and the exchange energy has the different sign.

Contents