Theory of Longitudinal Spin Fluctuations and the Antiferromagnetic Phase Transition in Chromium Metal

The wave-vector and temperature dependence of longitudinal spin fluctuation scattering in the itinerant model of antiferromagnetism is discussed. The simple random-phase-approximation model is shown to be consistent with existing neutron scattering experiments. A picture of the antiferromagnetic-to-paramagnetic phase transition being due to a "soft" longitudinal spin fluctuation mode coming down in energy at TN, as opposed to a disordering of local spins, is presented. Experimental results which support this view are discussed, and experiments are suggested to verify it further.