Charge and Spin Transport in Magnetic Nanowires

Abstract

The large interest in magnetic nanowires is mostly related to their possible application in magnetoelectronics. It was established experimentally that the magnetic domain walls (DWs) in very thin magnetic wires can affect substantially their resistance up to 1000% or even more (Chopra & Hua (2002)), (Rüster et al. (2003)). On the other hand, the magnetic DWs in nanowires can be effectively controlled by weak external magnetic field and by electric current pulses. The latter effect of current-induced DW motion opens the way for various applications. One of the most impressive advances in this direction is the development of race-tracking memory devices for fast storage and reading of information (Parkin et al. (2008)). A review of the properties of magnetic nanowires with domain walls has been presented recently in Ref. (Kläui (2008)). Several different phenomena have been in the scope of experimental and theoretical research, each of them being important for the use of magnetic nanowires in magnetoelectronics. The first one is the problem of transmission and reflection of electrons through the DW since this effect is mostly responsible for the magnetoresistivity. The other problem is related to the spin-transfer torque in magnetic nanowires and possible mechanisms of the current-induced DW motion. These mechanisms are responsible for effective current-induced control of the DW motion and correspondingly for current-induced variation of the resistance of magnetic nanowires. The third problem concerns the dynamics of the DWs motion since the dynamics are related to the possibility of fast current-induced control of the resistance. In this Chapter we review our main results of theoretical investigations into charge and spin transport properties in magnetic nanowires, mostly using some simplified models. Solving the models one can understand better the underlying physical mechanisms of the spin and charge transport in magnetic nanowires, that can be also used in computer simulations which should take into account real electronic and magnetic structure of a specific material. The details of our calculations and more information on the methods can be found in Refs.: (Dugaev et al. (2002)), (Dugaev et al. (2003)), (Dugaev et al. (2004)), (Dugaev et al. (2005)), (Araújo et al. (2006)), (Dugaev et al. (2006)), (Araújo et al. (2007)), (Dugaev et al. (2007)), (Sedlmayr et al. (2009)) and (Sedlmayr et al. (2010)).