title: Quantized magnetoresistance in atomic-size contacts.
abstract: When the dimensions of a metallic conductor are reduced so that they become comparable to the de Broglie wavelengths of the conduction electrons, the absence of scattering results in ballistic electron transport and the conductance becomes quantized. In ferromagnetic metals, the spin angular momentum of the electrons results in spin-dependent conductance quantization and various unusual magnetoresistive phenomena. Theorists have predicted a related phenomenon known as ballistic anisotropic magnetoresistance (BAMR). Here we report the first experimental evidence for BAMR by observing a stepwise variation in the ballistic conductance of cobalt nanocontacts as the direction of an applied magnetic field is varied. Our results show that BAMR can be positive and negative, and exhibits symmetric and asymmetric angular dependences, consistent with theoretical predictions.
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA. asokol@unlserve.unl.edu
authors.forename: Andrei
authors.initials: A
authors.lastname: Sokolov
authors.forename: Chunjuan
authors.initials: C
authors.lastname: Zhang
authors.forename: Evgeny Y
authors.initials: EY
authors.lastname: Tsymbal
authors.forename: Jody
authors.initials: J
authors.lastname: Redepenning
authors.forename: Bernard
authors.initials: B
authors.lastname: Doudin
mesh_terms: D003035:Cobalt / Q000737:chemistry* / Q000528:radiation effects; D008280:Magnetics; D008422:Materials Testing; D008839:Microelectrodes; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D011789:Quantum Theory
chemical_list: D003035:Cobalt