Stroboscopic XMCD–PEEM imaging of standing and propagating spinwave modes in permalloy thin-film structures

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• 作者：Frederik Wegelin ; Alex ; er Krasyuk ; Hans-Joachim Elmers ; Sergej A. Nepijko ; Claus M. Schneider ; Gerd Schö ; nhense
• 关键词：PEEM ; XMCD ; Spintronics ; Magnetic domain ; Manganite ; Thin film
• 刊名：Surface Science
• 出版年：2007
• 出版时间：15 October 2007
• 年：2007
• 卷：601
• 期：20
• 页码：4694-4699
• 全文大小：750 K

文摘

Using synchrotron-based stroboscopic photoemission electron microscopy with X-ray circular dichroism as contrast method, we have investigated the high-frequency response of permalloy thin-film structures. Standing precessional modes have been studied in rectangular elements (16 × 32 μm<sup>2sup>, 10 nm thick) with a high time resolution of about 15 ps in the low-α mode of BESSY. With increasing amplitude of the applied magnetic AC field the particle is driven from an initial symmetric Landau flux-closure state into an asymmetric state and finally into a single-domain state magnetized perpendicular to the applied field <strong>Hstrong><sub>ACsub>. The electromagnetic microwave field thus can induces a net magnetization in a small particle. This behaviour is a result of the constant throughput of energy (open system) that allows for an increase of local order, contrary to the usual increase on entropy in closed systems. A propagating spinwave in an ultrathin elliptical particle (semi axes 6 × 12 μm<sup>2sup>, 3 nm thick) was observed in a snapshot series with 25 ps time increment. The phase front of the spinwave with large precessional angle (bright contrast) propagates with a velocity of 8100 m/s, i.e. much faster than typical domain wall velocities in permalloy.