Problem of bound states in ferromagnets with spinS = 1/2

The problem of the bound states in the Heisenberg ferromagnet of spinS = 1/2 is considered using the exact boson representation. The results are identical with those obtained with the spin operators but the present approach does not suffer from the inconsistencies inherent to the spin-operator approach. Also it is shown that other existing boson representations (Marumori, Dyson) are inadequate for the treatment of the bound states of the Heisenberg ferromagnet with spinS = 1/2.