Dresden 2003 – scientific programme
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MA: Magnetismus
MA 25: Spinabh
ängige Transportph
änomene I
MA 25.6: Talk
Thursday, March 27, 2003, 16:30–16:45, HSZ/04
Magnetic tunnel junctions with Y2O3 barrier — •Theodoros Dimopoulos1,2, Günter Gieres1, Joachim Wecker1, Yuansu Luo2, and Konrad Samwer2 — 1Siemens AG, Corporate Technology, Erlangen — 2Universität Göttingen, I. Physikalisches Institut
In the last two decades significant progress has been achieved on the elaboration of magnetic heterojunctions of the ferromagnet(FM)/insulator(I)/ferromagnet(FM) type, where spin dependent tunneling is manifested. In their vast majority, the junctions employ Al oxide as insulator (tunnel barrier) and 3d FM as electrodes.
In the present work we introduce Y2O3 as tunnel barrier. Magnetic tunnel junctions of the following stack have been fabricated by sputtering: SiO2/buffer/IrMn/CoFe /Y2O3/CoFe/NiFe/capping. Y2O3 forms a sharp and smooth interface with the underlying FM electrode of the junction, as shown by small angle X-ray diffraction measurements and by atomic force microscopy images of the barrier’s surface, from which an RMS roughness as low as 0.15 nm has been extracted. Microfabricated junctions present tunnel magnetoresistance (TMR) ratios of ∼ 27% at room temperature and ∼ 45% at 5K. The variation of the TMR ratio for different FM electrodes has been studied. The spin dependent junction conductance has been measured as a function of the temperature (from 4K to 290K) and of the bias voltage. From these dependencies we will focus on the possible transport contributions related to elastic and inelastic mechanisms (scattering on magnons, impurities in the barrier,etc) for the Y2O3-based junctions. This work is partially supported by the Sonderforschungsbereich SFB 602, University of Göttingen.