Coherence and modality of driven interlayer-coupled magnetic vortices.
The high-frequency dynamics of mode-coupled magnetic vortices have generated great interest for spintronic technologies, such as spin-torque nano-oscillators. While the spectroscopic characteristics of vortex oscillators have been reported, direct imaging of driven coupled magnetic quasi-particles is essential to the fundamental understanding of the dynamics involved. Here, we present the first direct imaging study of driven interlayer coaxial vortices in the dipolar- and indirect exchange-coupled regimes. Employing in situ high-frequency excitation with Lorentz microscopy, we directly observe the steady-state orbital amplitudes in real space with sub-5 nm spatial resolution. We discuss the unique frequency response of dipolar- and exchange-coupled vortex motion, wherein mode splitting and locking demonstrates large variations in coherent motion, as well as detail the resultant orbital amplitudes. This provides critical insights of the fundamental features of collective vortex-based microwave generators, such as their steady-state amplitudes, tunability and mode-coupled motion.
Department of Condensed Matter Physics, Brookhaven National Laboratory, Upton, New York 11973, USA.
J F
JF
Pulecio
Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, Switzerland.
P
P
Warnicke
1] Department of Condensed Matter Physics, Brookhaven National Laboratory, Upton, New York 11973, USA [2] Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA.
S D
SD
Pollard
National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, USA.
D A
DA
Arena
Department of Condensed Matter Physics, Brookhaven National Laboratory, Upton, New York 11973, USA.
Y
Y
Zhu
D003198:Computer Simulation; D008279:Magnetic Resonance Imaging; D008280:Magnetics / Q000379:methods*; D046529:Microscopy, Electron, Transmission; D008872:Microwaves; D036103:Nanotechnology / Q000379:methods*