Dresden 2006 – wissenschaftliches Programm

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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 20.44: Poster

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

Amorphous leads and tunneling magnetoresistance — •Martin Gradhand, Christian Heiliger, and Ingrid Mertig — Martin Luther University, FB Physik, FG Theorie, D-06099 Halle, Germany

High tunnelling magnetoresistance ratios up to 230 % have been obtained recently [1] for magnetic tunnel junctions consisting of amorphous CoFeB leads separated by a crystalline MgO barrier. The idea of this contribution is to understand the spin-polarization of the tunnelling current and the TMR for a system composed of a crystalline MgO barrier sandwiched between two amorphous Fe leads. The role of a crystalline Fe spacer between the leads and the barrier is investigated. The amorphous Fe leads were simulated by fitting the pair-correlation function of a super cell by a reverse Monte-Carlo algorithm. The performance of the algorithm was tested for different initial configurations (bcc, fcc, sc, and random) and a varying number of atoms in the super cell. The electronic structure of the system was calculated self-consistently using a linear muffin-tin orbital (LMTO) method [2]. The spin-polarized tunnelling current is obtained by means of the Kubo formula using the scheme of Baranger and Stone [3].

[1] D. D. Djayaprawira et al., Appl. Phys. Lett. 86, 092502 (2005)

[2] http://www.fkf.mpg.de/andersen/

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