Significant Modulation of Vortex Resonance Spectra in a Square-Shape Ferromagnetic Dot

Abstract

The resonance property of a magnetic vortex contained within a micron-sized square Py dot was detected using an amplitude-modulated magnetic field excitation technique. We found a significant modulation of the resonant spectra as the external magnetic field changes. The Lorentzian-like spectrum changes from a peak to a dip via a transition of anti-Lorentzian-like spectra. By conducting the micromagnetic simulations, we confirmed that the transition behavior results from the unusual resistance change depending on the vortex core center position. Additionally, the power dependence of the anti-Lorentzian-like spectra revealed a fairly persistent coexistence of peak and dip. Thus, the tunable spectra suggest one way to develop an integratable radiofrequency microcircuits.

Magnetic vortex polarity reversal induced gyrotropic motion spectrum splitting in a ferromagnetic disk

“…The intricate dynamics behind this transition behavior can be ascribed to the atypical resistance alterations contingent upon the central positioning of the vortex core. This phenomenon has been extensively detailed and rationalized in our recent work [43]. Furthermore, when we modulate the RF power, elevating it from −20 dBm to a higher −10 dBm, we observe a nuanced alteration in the spectral characteristics.…”

“…Figure 4(a) delineates the core trajectories of the singular vortex structure at RF power levels of −20 dBm and −10 dBm, superimposed on a contour map depicting magnetoresistance within the Permalloy disk. Time-dependent AMR, calculated under the constraint of uniform current density, is presented in figures 4(b) and (c) [43,47]. Remarkably, at an RF power of −20 dBm, the vortex core manifests stable oscillatory behavior.…”

“…The dynamic properties of the magnetic vortices were detected using lock-in electric measurement technique while the vortex core is excited by the amplitude-modulated Oersted field generated accurately by each Cu electrode [40,43]. Figure 1(a) demonstrates that during the measurement, an inplane external magnetic field was applied along the chain of Py disks, causing the vortex core to shift perpendicular to the direction of the magnetic field [44].…”