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 μm 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.
@article{arxiv.1504.01512,
title = {Generation of coherent spin-wave modes in Yttrium Iron Garnet microdiscs by spin-orbit torque},
author = {Martin Collet and Xavier De Milly and Olivier D'Allivy-Kelly and Vladimir V. Naletov and Rozenn Bernard and Paolo Bortolotti and Vladislav Demidov and Sergej Demokritov and Jose Luis Prieto and Manuel Muñoz and Abdelmadjid Anane and Vincent Cros and Grégoire De Loubens and Olivier Klein},
journal= {arXiv preprint arXiv:1504.01512},
year = {2016}
}