Fast current-induced domain-wall motion controlled by the Rashba effect

• Published in: Nature materials 2011-06, Vol.10 (6), p.419-423
• Main Authors: Miron, Ioan Mihai, Moore, Thomas, Szambolics, Helga, Buda-Prejbeanu, Liliana Daniela, Auffret, Stéphane, Rodmacq, Bernard, Pizzini, Stefania, Vogel, Jan, Bonfim, Marlio, Schuhl, Alain, Gaudin, Gilles
• Format: Article
• Language: English
• Subjects: 639/301/357/1016; 639/301/357/995; 639/301/357/997; Biomaterials; Chemistry and Materials Science; Condensed Matter; Condensed Matter Physics; Current density; Devices; Focusing; Instability; Inversions; letter; Logic; Magnetism; Materials Science; Motion control; Nanotechnology; Nanowires; Optical and Electronic Materials; Other; Physics; Walls
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat3020

Although magnetic domain walls could one day be used for information storage, the current challenges to their use are the irreproducibility of their displacement and the limits to their maximum speed. It is now shown that the Rashba effect can be used to provide a solution to both these issues. The propagation of magnetic domain walls induced by spin-polarized currents 1 , 2 , 3 , 4 , 5 has launched new concepts for memory and logic devices 6 , 7 , 8 . A wave of studies focusing on permalloy (NiFe) nanowires 9 has found evidence for high domain-wall velocities (100 m s −1 ; refs  10 , 11 ), but has also exposed the drawbacks of this phenomenon for applications. Often the domain-wall displacements are not reproducible 12 , their depinning from a thermally stable position is difficult 13 and the domain-wall structural instability (Walker breakdown 14 , 15 ) limits the maximum velocity 10 . Here, we show that the combined action of spin-transfer and spin–orbit torques offers a comprehensive solution to these problems. In an ultrathin Co nanowire, integrated in a trilayer with structural inversion asymmetry (SIA), the high spin-torque efficiency 16 facilitates the depinning and leads to high mobility, while the SIA-mediated Rashba field 17 , 18 , 19 controlling the domain-wall chirality stabilizes the Bloch domain-wall structure. Thus, the high-mobility regime is extended to higher current densities, allowing domain-wall velocities up to 400 m s −1 .