Spin transport in magnetic multilayers

Abstract

We study by extensive Monte Carlo simulations the transport of itinerant spins travelling inside a multilayer composed of three ferromagnetic films antiferromagnetically coupled to each other in a sandwich structure. The two exterior films interact with the middle one through non magnetic spacers. The spin model is the Ising one and the in-plane transport is considered. Various interactions are taken into account. We show that the current of the itinerant spins going through this system depends strongly on the magnetic ordering of the multilayer: at temperatures T below (above) the transition temperature Tc, a strong (weak) current is observed. This results in a strong jump of the resistance across Tc. Moreover, we observe an anomalous variation, namely a peak, of the spin current in the critical region just above Tc. We show that this peak is due to the formation of domains in the temperature region between the low-T ordered phase and the true paramagnetic disordered phase. The existence of such domains is known in the theory of critical phenomena. The behavior of the resistance obtained here is compared to a recent experiment. An excellent agreement with our physical interpretation is observed. We also show and discuss effects of various physical parameters entering our model such as interaction range, strength of electric and magnetic fields and magnetic film and non magnetic spacer thicknesses.

Monte Carlo study of the spin transport in magnetic materials

“…Note that unlike in the previous works [30,31] where the lattice spin configuration is frozen while calculating the resistivity, we use here several thousands of configurations in each of which the resistivity is averaged with many thousands of passages. In our previous works, though the overall number of MC steps per spin was as high as in this work, the fact that we have used only a dozen lattice configurations for resistivity calculation has shown strong fluctuations in the result.…”

“…[28] and [29]. In spite of these intensive investigations, except our works [30,31], there have been no Monte Carlo (MC) simulations performed regarding the temperature dependence of the spin transport. In these works , we have investigated by MC simulations the effects of magnetic ordering on the spin current in magnetic multilayers.…”

Theory and simulation of spin transport in antiferromagnetic semiconductors: Application to MnTe

“…In our previous work [17][18][19] we studied the spin current in ferromagnetic thin films. The behavior of the spin resistivity as a function of T has been shown and explained as an effect of magnetic domains formed in the proximity of the phase transition point.…”

SPIN RESISTIVITY IN THE FRUSTRATED J1 - J2 MODEL

“…Our results for ferromagnets are in agreement with other theories, in particular the existence of the peak at T C and its dependence on the strength of magnetic field and density of itinerant spins. 8,9 In unfrustrated antiferromagnets, there has been a few investigations. Some theories predicted the absence of a sharp peak at T C .…”