Spin Waves in Itinerant Electron Antiferromagnet

In the Skater model for itinerant electron antiferromagnets, spin wave spectrum is calculated by taking into account long range Coulomb interactions. The method of normal mode is used in the random phase approximation in order to get various modes of spin waves, i.e., acoustical and polar spin waves. It is shown that polar spin waves exist when the inter-atomic Coulomb interaction is sufficiently strong. Furthermore, the velocity of the acoustical spin wave is shown to be reduced by the inter-atomic Coulomb and exchange interactions. The magnitudes of these reductions are numerically estimated for an antiferromagnet with b.c.c. structure. It is shown that the observed result of the spin wave velocity for Cr is explained by these numerical results.