Influence of magnetic field offsets on the resistance of magnetic barriers in two-dimension.pdf

a r X i v : 0 7 0 8 .2 0 3 2 v 1 [ c o n d - m a t .m e s - h a l l ] 1 5 A u g 2 0 0 7 Influence of magnetic field offsets on the resistance of magnetic barriers in two-dimensional electron gases S. Hugger, M. Cerchez, H. Xu, and T. Heinzel? Heinrich-Heine-Universita?t, Universita?tsstr. 1, 40225 Du?sseldorf, Germany (Dated: February 1, 2008) Magnetic barriers in two-dimensional electron gases are shifted in B space by homogeneous, per- pendicular magnetic fields. The magnetoresistance across the barrier shows a characteristic asym- metric dip in the regime where the polarity of the homogeneous magnetic field is opposite to that one of the magnetic barrier. The measurements are in quantitative agreement with semiclassical simulations, which reveal that the magnetoresistance originates from the interplay of snake orbits with E × B drift at the edges of the Hall bar and with elastic scattering. PACS numbers: 73.23.-b,75.70.Cn I. INTRODUCTION The transport properties of two-dimensional electron gases (2DEGs) in spatially varying magnetic fields show a rich phenomenology, and several interesting effects have been reported recently. For example, magnetic superlattices1,2 show commensurability oscillations in the magnetotransport, while giant magnetoresistance effects have been found on one-dimensional magnetic arrays2. Also, a variety of single magnetic nanostructures have been investigated via their influence on the 2DEG, like resistance resonances along magnetic edge states3, the experimental realization of magnetic waveguides4, or the demonstration of Hall sensing5,6. A magnetic nanostruc- ture of elementary character, known as single magnetic barrier - MB, is formed by the highly localized perpen- dicular (z-) component Bfz of the magnetic fringe field in a 2DEG below the edge of a ferromagnetic film mag- netized in transport (x-) direction7,8,9,10,11,12,13,14,15. Al- ternatively, such a structure can be defined in a 2DEG with a graded step16. Various aspect