Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 40: Poster II: Bio- and Molecular Magnetism (1-9); Magnetic Coupling Phenomena/Exchange Bias (10-15); Magnetic Particlicles and Clusters (16-29); Micro and Nanostructured Magnetic Materials (30-51); Multiferroics (52-64); Spin Injection in Heterostructures (65-67); Spin-Dyn./Spin-Torque (68-93); Spindependent Transport (94-108)
MA 40.100: Poster
Freitag, 27. März 2009, 11:00–14:00, P1A
Annealing behaviour of CoFeB/MgO/CoFeB magnetic tunnel junctions — Sebastian Ringer1,2, Michael Vieth2, Ludwig Bär2, Manfred Rührig2, and •Günther Bayreuther1 — 1Universität Regensburg, 93040 Regensburg, Germany — 2Siemens AG, Corporate Technology CT T MM1, 91050 Erlangen, Germany
With CoFeB/MgO/CoFeB magnetoresistive tunnel junctions, annealing is commonly used to increase the TMR ratio. The annealing process simultaneously affects the antiferromagnetic pinning layer as well as the tunnel barrier and the ferromagnetic contacts. In particular, the role of diffusion of B into the MgO barrier has been considered recently. By a systematic variation of annealing time and temperature the present study aims to achieve a better understanding of the relevant diffusion processes and an optimization of the annealing procedures. Junctions with a barrier thickness of 1.5 nm showed a TMR ratio of 30% at room temperature before annealing which increased to a maximum value of 150% after annealing for 4 h at 350° C. Measurement of the high resistance state (i.e. for antiparallel magnetizations), the low resistance state (parallel magnetizations) and the TMR ratio versus annealing time at different temperatures allows for the calculation of temperature dependent time constants and activation energies of the processes involved. A comparison of room temperature and low temperature resistance values is used to separate different effects of the annealing process.