Spin-Wave Excitations of Half-Filled Kondo Lattice Model

The spin excitations in the antiferromagnetic phase of half-filled Kondo lattice model are studied by means of the decoupling approximation for spin Green's function. The spin-wave spectrum is calculated as a function of Kondo coupling, and this is used to calculate the thermodynamic quantities at low temperatures. The N\'{e}el temperature of the form $T_{\rm N}=0.087{J}^2\ln{(1/J)}$ is obtained for the 3-dimensional case in the weak-coupling limit. It is pointed out that the ratio of the spin-wave velocity to the N\'{e}el temperature $v_s/T_{\rm N}$ is enhanced as the Kondo coupling becomes small, reflecting the long-range nature of effective interactions between localized spins.