Giant magnetoresistance induced by magnetic barriers

Effect of edge transmission and elastic scattering on the resistance of magnetic barriers: Experiment and theory

“…As a test simulation, we have turned off all scattering and set the electric field at the edges to zero, thereby simulating a ballistic magnetic barrier which extends to infinity in the y direction. In this case, the numerical results closely match the corresponding analytical expression 21 and reproduce the critical angle of incidence for which the magnetic barrier closes to an accuracy of 1 degree. For a comparison of the simulations with the experiments, the magnetization trace M͑B͒ shown in the inset of Fig.…”

“…Previous studies have already shown that both edge transmission and scattering in the barrier region are relevant. 21,23 Here, we build on these results and discuss in detail how the resistance of tunable magnetic barriers depends upon the E ϫ B drift at the edges, on the elastic scat-FIG. 1.…”

Resonant reflection at magnetic barriers in quantum wires

“…Here, we use the recursive Greens function (RGF) technique to investigate the structure and the conductance of a single MB that forms in a quantum wire (QWR) below the edge of a ferromagnetic film. The barrier shapes are adapted from typical experimental conditions [12,13,14,15,16,17,18]. We find that for smooth barriers with a large spatial extension, the number of transmitted modes drops stepwise and without resonances as the barrier amplitude increases or, correspondingly, the Fermi energy is reduced.…”

“…Localized magnetic fields that are oriented perpendicular to a quantum film [1,2] or a quantum wire [3,4,5,6,7,8,9,10,11], which are furthermore strongly localized in transport (x -) direction and homogeneous in the transverse (y-) direction are known as magnetic barriers (MBs). They can be realized experimentally by ferromagnetic films on top of a two-dimensional [12,13,14,15,16,17,18] or quasi one-dimensional electron gas residing in a semiconductor heterostructure: magnetizing the ferromagnetic film in x -direction results in a magnetic fringe field with a z -component localized at the edge of the film that extends along the y-direction. Transport experiments on MBs in two-dimensional electron gases show a pronounced positive magnetoresistance as a function of the MB amplitude [14,15,16,17,18], which can be interpreted quantitatively in a classical picture [15,18], where the MB acts as a filter with a transmission probability that depends upon the angle of incidence of the electrons.…”

“…They can be realized experimentally by ferromagnetic films on top of a two-dimensional [12,13,14,15,16,17,18] or quasi one-dimensional electron gas residing in a semiconductor heterostructure: magnetizing the ferromagnetic film in x -direction results in a magnetic fringe field with a z -component localized at the edge of the film that extends along the y-direction. Transport experiments on MBs in two-dimensional electron gases show a pronounced positive magnetoresistance as a function of the MB amplitude [14,15,16,17,18], which can be interpreted quantitatively in a classical picture [15,18], where the MB acts as a filter with a transmission probability that depends upon the angle of incidence of the electrons. Moreover, Peeters et al [1] studied the energy spectrum and the transmission properties of MBs with a rectangular profile in a two-dimensional electron gas by analytical means.…”