Stoner excitations

Besides spin waves, another type of excitation in a metal can reduce its magnetization. Electrons at the Fermi level can be excited from filled states in the majority-spin band to empty states in the minority-spin band. If the initial state has wavevector k and the final state has wavevector k − q, an excitation of wavevector q is produced. The energy of the excitation is given by

At q = 0, these excitations require the full exchange splitting Δ_ex , but at finite q there is a broad continuum of Stoner excitations.