Spin transport in magnetic multilayers

TL;DR

This study uses Monte Carlo simulations to analyze how spin transport in magnetic multilayers varies with temperature, revealing a resistance jump at the transition temperature and a peak in spin current due to domain formation.

Contribution

It provides a detailed simulation-based analysis of spin transport in multilayer structures, highlighting the impact of magnetic ordering and domain formation on resistance and spin current behaviors.

Findings

Resistance exhibits a sharp jump at the transition temperature.

A peak in spin current occurs just above the critical temperature.

Behavior aligns well with recent experimental observations.

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 $T_c$, a strong (weak) current is observed. This results in a strong jump of the resistance across $T_c$. Moreover, we observe an anomalous variation, namely a peak, of the spin current in the critical region just above $T_c$. 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.