Electronic Structure Of Dilute Itinerant Electrons On A Ferromagnetic Domain Wall

There are mainly two models explaining magnetism, one is based on localised spin, such as Heisenberg Model; the other one is based on itinerant electrons, such as Stoner Model. Suhl and Abrikosov proposed a model which involves the exchange interaction of localised spin and itinerant electrons for coexisting ferromagnetism and superconductivity; Barnes,Maekawa proposed a similar model to explain the displace-ment of a domain wall in the presence of small current.Inspired by their work, besides considering the exchange interaction of localised spin and itinerant electrons, we also consider the interaction between localised spins, and then give our hamiltonian for two-dimension system which is suggested by the two-dimensional domain wall, through our model, we study the electronic structure.In chapter one, the works by Suhl and Barnes,Maekawa are introduced, according to their argument, we introduced our model.In chapter two, we mainly discuss the theoretical methods for our hamiltonian. We adopt linearised spin wave approximation and Holstein-Primakoff transformation, and rewrite our hamiltonian with the creation and annihilation operator of electrons and magnons. Then we introduced finite temperature Green's function. The reason we adopt finite temperature Green's function is that its perturbation theory provides ture description of interaction system. When temperature T goes to the zero limit, this method gives true ground state of system under any values of coupling constant.In chapter three, we study the eletronic structure when taking localised spin into consideration. Localised spin lead spin-up and spin-down electron energy band sepa-rated. When there are not many electrons in the system, the Fermi surface of spin-up and spin-down electrons are circles, this paper gives demonstration both mathemati-cally and graphically.In chapter four, we study the the modified selfenergy of itinerant electrons by magnons. The polarisation of spin-up and spin-down electrons is strengthened when J＞0, and is weakened when J＜0.We also studied itinerant electron's dispersion re-lation through spectrum function of Green's function, and energy distribution function and momentum distribution function.