On the theory of the low-temperature spontaneous magnetization of ferromagnetic metals

Abstract
The temperature variation of the low-temperature spontaneous magnetization ξ of a ferromagnetic metal is obtained from assumptions that are consistent with the usual band theory. The second-quantized Hamiltonian for the system is taken to contain electronic energy band terms as well as Coulomb and exchange energy terms. The Green function method is used. It is shown that spin-wave excitations of small wave vector k exist with energies proportional to k 2 , from which it is deduced that ξ = ξ 0 {1— γ T 3/2 ), with ξ 0 dependent on the average number of electrons per band. An analytical expression is found for the constant γ which differs from that obtained in the Heisenberg model.

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