Band-Structure Effects in Itinerant Antiferromagnetism

The effect of imperfect "nesting" of the band structure on itinerant antiferromagnetism is considered. A model band structure with spherical electron and hole pockets of unequal radii and a "nonmagnetic" reservoir is examined. A first-order commensurate-incommensurate transition is found, but the paramagnetic transition remains second order. The influence of generalized Kohn anomalies on the transition is investigated, and it is found that though they lead to anomalous behavior in the limit of vanishing antiferromagnetism, there is no change in the order of the transition.