Excitation in two-dimensional diluted ferromagnet with an anisotropic exchange interaction

Excitations in a two-dimensional diluted ferromagnet with an anisotropic exchange interaction are studied by using the moment expansion method. Spectra at various points in the Brillouin zone and the imaginary part of the Green function at a central site (equivalent to the state density) are presented over the whole range of the concentration of non-magnetic ions, by analysing a moment expansion using both the Pade approximation and the continued-fraction representation. The exponential (Lifschitz) tail and the response from the dangling bonds are observed. Comparison with experiments is also made.