The magnetic phase transition is experimentally known to give rise to an anomalous temperature dependence of the electron resistivity in ferromagnetic crystals. Phenomenological theories based on the interaction between itinerant electron spins and lattice spins have been suggested to explain these observations. In this paper, we show by extensive Monte Carlo ͑MC͒ simulation the behavior of the resistivity of the spin current calculated as a function of temperature ͑T͒ from low-T ordered phase to high-T paramagnetic phase in a ferromagnetic film. We analyze, in particular, the effects of film thickness, surface interactions, and different kinds of impurities on the spin resistivity across the critical region. The origin of the resistivity peak near the phase transition is shown to stem from the existence of magnetic domains in the critical region. In this paper, we also formulate a theory based on the Boltzmann equation in the relaxation-time approximation. This equation can be solved by using numerical data obtained by our simulations. We show that our theory is in a good agreement with our MC results. Comparison with experiments is discussed.

In this paper we study the spin transport in frustrated antiferromagnetic FCC films by Monte Carlo simulation. In the case of the Ising spin model, we show that the spin resistivity versus temperature exhibits a discontinuity at the phase transition temperature: an upward jump or a downward fall, depending on how many parallel and antiparallel localized spins interacting with a given itinerant spin. The surface effects as well as the difference of two degenerate states on the resistivity are analyzed. A comparison with nonfrustrated antiferromagnets is shown to highlight the frustration effect. We also show and discuss the results of the Heisenberg spin model on the same lattice.