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arXiv · 1504.01512

Generation of coherent spin-wave modes in Yttrium Iron Garnet microdiscs by spin-orbit torque

Martin Collet·Xavier De Milly·Olivier D'Allivy-Kelly·Vladimir V. Naletov·Rozenn Bernard·Paolo Bortolotti·Vladislav Demidov·Sergej Demokritov·Jose Luis Prieto·Manuel Muñoz·Abdelmadjid Anane·Vincent Cros·Grégoire De Loubens·Olivier Klein
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Abstract

Spin-orbit effects [1-4] have the potential of radically changing the field of spintronics by allowing transfer of spin angular momentum to a whole new class of materials. In a seminal letter to Nature [5], Kajiwara et al. showed that by depositing Platinum (Pt, a normal metal) on top of a 1.3 $\mu$m thick Yttrium Iron Garnet (YIG, a magnetic insulator), one could effectively transfer spin angular momentum through the interface between these two different materials. The outstanding feature was the detection of auto-oscillation of the YIG when enough dc current was passed in the Pt. This finding has created a great excitement in the community for two reasons: first, one could control electronically the damping of insulators, which can offer improved properties compared to metals, and here YIG has the lowest damping known in nature; second, the damping compensation could be achieved on very large objects, a particularly relevant point for the field of magnonics [6,7] whose aim is to use spin-waves as carriers of information. However, the degree of coherence of the observed auto-oscillations has not been addressed in ref. [5]. In this work, we emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current. This requires to reduce both the thickness and lateral size in order to reach full damping compensation [8] , and we show clear evidence of coherent spin-orbit torque induced auto-oscillation in micron-sized YIG discs of thickness 20 nm.

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Martin Collet, Xavier De Milly, Olivier D'Allivy-Kelly, Vladimir V. Naletov, Rozenn Bernard, Paolo Bortolotti, Vladislav Demidov, Sergej Demokritov, Jose Luis Prieto, Manuel Muñoz, Abdelmadjid Anane, Vincent Cros, Grégoire De Loubens, Olivier Klein. 2015-04-07. Generation of coherent spin-wave modes in Yttrium Iron Garnet microdiscs by spin-orbit torque. https://doi.org/10.1038/ncomms10377

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