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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.45: Poster

Dienstag, 28. März 2006, 15:15–19:15, P1

Ballistic magnetoresistance in Ni single-atom contacts — •Steven Walczak, Michael Czerner, and Ingrid Mertig — Martin Luther University, FB Physik, FG Theoretische Physik, D-06090 Halle

Extraordinary large ballistic magnetoresistance has been measured in Ni single-atom contacts [1,2]. The experimental results are still in contradiction to other experimental [3] and to theoretical results in the coherent limit of transport [4].

This contribution aims to explain the strong changes of resistance under the influence of an external magnetic field by means of a rotating magnetic Ni particle in the constriction.

The electronic structure of the Ni particle in the constriction is calculated selfconsistently using the Korringa-Kohn-Rostoker method. Different orientations of the Ni particle in the constriction caused by an external magnetic field are considered. Transport through the Ni particle is described by means of the Landauer approach in the formulation of Baranger and Stone [5]. It will be shown that small rearrangements of a Ni particle under the influence of an external magnetic field can change the conductance by a few G_o and can cause BMR ratios of several hundred percent.

[1] N. Garcìa et al., Phys. Rev. Lett. 82, 2923 (1999)

[2] M. R. Sullivan et al., Phys. Rev. B 71, 024412 (2005)

[3] M. Viret et al., Phys. Rev. B 66, 220401 (2002)

[4] A. Bagrets et al., cond-mat/0510073 (2005)

[5] H. U. Baranger and A. D. Stone, Phys. Rev. B 40, 8169 (1989)