Spin wave theory of amorphous ferromagnets

A spin wave theory of amorphous ferromagnets is studied. The long wavelength spin waves can be clearly defined in amorphous states, since the inverse lifetime of the state is very small in comparison with the frequency of the spin waves. From the instability of the ferromagnetic ground state with respect to the formation of long wavelength spin waves, a criterion for the existence of amorphous ferromagnets is studied.