Electrical conductivity and magnetic order in the single-band Hubbard model

A Modified Alloy Analogy (MAA) for the single-band Hubbard model is used to investigate the interplay of ferromagnetic order and electrical conductivi ty in a system of itinerant band electrons. The alloy analogy is evaluated within the framework of the Coherent Potential Approximation (CPA). The ten sor conductivity, normally a two-particle Green function, can be represente d by single-particle terms if CPA-consistent approaches are applied [B.Veli cky;, Phys. Rev. 184, 614 (1969)]. The MAA is used far fee and bcc lattices . Spontaneous ferromagnetism appears in the fee lattice for a more than hal f-filled energy band (1 < n < 2). In the bcc lattice collective order is re stricted to a small n-region, The electrical conductivity is investigated f or different Coulomb strengths U as function of band occupation n and tempe rature T. The conductivity turns out to be substantially higher in the ferr omagnetic than in the paramagnetic phase, even diverging in the case of fer romagnetic saturation (T --> 0), where electron-electron scattering is excl uded. Majority-spin carriers contribute the main part to the current in the ferromagnetic phase. The electrical resistivity exhibits a power-like low- temperature behavior becoming critical at Tc. Formal similarity to the spin disorder resistivity of local moment systems is observed.