Magnetic vortex core reversal by excitation of spin waves

Abstract

Micron-sized magnetic platelets in the flux-closed vortex state are characterized by an in-plane curling magnetization and a nanometer-sized perpendicularly magnetized vortex core. Having the simplest non-trivial configuration, these objects are of general interest to micromagnetics and may offer new routes for spintronics applications. Essential progress in the understanding of nonlinear vortex dynamics was achieved when low-field core toggling by excitation of the gyrotropic eigenmode at sub-GHz frequencies was established. At frequencies more than an order of magnitude higher vortex state structures possess spin wave eigenmodes arising from the magneto-static interaction. Here we demonstrate experimentally that the unidirectional vortex core reversal process also occurs when such azimuthal modes are excited. These results are confirmed by micromagnetic simulations, which clearly show the selection rules for this novel reversal mechanism. Our analysis reveals that for spin-wave excitation the concept of a critical velocity as the switching condition has to be modified.

Spin wave mediated unidirectional vortex core reversal by two orthogonal monopolar field pulses: The essential role of three-dimensional magnetization dynamics

“…It has been demonstrated that the vortex core polarity can be dynamically reversed by exciting one of the eigenmodes of the vortex structure, i.e., the gyrotropic mode [1][2][3][4] or dipolar spin-wave modes. [5][6][7] For the vortex gyrotropic mode G 0 , the vortex core performs a translational motion with frequencies in the range of 100 MHz to 1 GHz (depending on the disk dimensions and the material of the disk). 8 Dipolar spin-wave modes have frequencies in the GHz range and describe dynamic excitations of the planar part of the vortex structure.…”

Efficient focusing of 8 keV X-rays with multilayer Fresnel zone plates fabricated by atomic layer deposition and focused ion beam milling

“…The utilization of focused X-rays has spread continuously over recent decades and includes applications such as imaging, chemical analysis (Sakdinawat & Attwood, 2010) and time-resolved investigation by exploiting pulses of synchrotron radiation (Kammerer et al, 2011;Van Waeyenberge et al, 2006;Saes et al, 2003). In contrast to electron microscopy, X-ray microscopy provides high penetration depth and enables three-dimensional imaging of complete cells (Vogt et al, 2000), large alive biological samples (Olendrowitz et al, 2012) and in situ investigation under extreme conditions (Fife et al, 2012).…”

Advanced magneto-optical microscopy: Imaging from picoseconds to centimeters - imaging spin waves and temperature distributions (invited)

“…This is due to the excitation of spin wave modes from out-of-plane magnetization components from the central vortex. 17 The spin waves confine at higher field frequencies up to 4 GHz (Fig. 10(g) and 10(h)).…”

“…The spin waves can be excited by different means, for instance not only by using microwave antennas, 14 but also from domain wall oscillations 15,16 and magnetic vortex reversal. 17 Here, we present a proof of the generation of spin waves from flux-closed vortex configuration via time-resolved MOKE imaging. Fig.…”