Dresden 2009 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 7: Spin-Dynamics/ Spin-Torque II

MA 7.4: Vortrag

Montag, 23. März 2009, 16:00–16:15, HSZ 04

Impact of lateral size of nanopillars on spin wave spectra in magnetic tunnel junctions — •Annerose Helmer¹, Sven Cornelissen^2,3, Thibaut Devolder¹, Joo-Von Kim¹, Paul Crozat¹, Maaike Op de Beeck², Liesbet Lagae^2,4, and Claude Chappert¹ — ¹Institut d´ Electronique Fondamentale, CNRS UMR 8622, Bât. 220, Université Paris-Sud 11, 91405 Orsay, France — ²IMEC, NextNS, Kapeldreef 75, 3001 Leuven, Belgium — ³ESAT, KU Leuven, Leuven, Belgium — ⁴Natuurkunde en Sterrenkunde, KU Leuven, Leuven, Belgium

As dynamic eigenexcitations of a magnetic system, thermally excited spin waves constitute an excellent probe for the intrinsic magnetic properties of nanopillar devices, such as MRAM. In particular, they provide information on the spatial orientation of the magnetization in the different layers of the pillar. We have studied spin wave spectra (mode frequency versus magnetic field) in rectangular shaped nanopillars of lateral dimensions 50 x 100, 75 x 140, and 100 x 200 nm2, patterned from MgO-based magnetic tunnel junctions, which were deposited at Singulus Technologies AG. The devices were subjected to in-plane magnetic fields either along the long edge (easy axis) or the short edge (hard axis) of the rectangle. For both field directions the spectra become more complex with larger lateral pillar sizes: the number of modes increases, their relative intensity changes, while the spectra become progressively deformed - phenomena, which can be explained by the formation of edge domains. Moreover, there is clear evidence that not even for the smallest pillar size the magnetization is uniform.