Inductive detection of magnetic vortex gyration

Abstract

Vortex cores in Landau-domain patterns are resonantly excitable by alternating magnetic fields in the subgigahertz regime. We present a highly sensitive method to detect the vortex gyration in single micrometer-sized elements spectroscopically by measuring spectra of induction voltages caused by the stray fields of a single ferromagnetic square exposed to an alternating Oersted field. A distinct change of the induction voltage is observed around the resonance frequency of the vortex core. The shape of the measured spectra deviates from Lorentzian profiles due to voltages induced by magnetic fringing fields of the exciting currents. An analytical description of the measured spectra is given. A characteristic frequency shift in external magnetic fields proves that signals detected by the induction sensor originate from the dynamically excited Landau-domain pattern. The measurements on a single square are compared with measurements on an ensemble of uniform squares.

Chirality-mediated bistability and strong frequency downshifting of the gyrotropic resonance of a magnetic vortex due to dynamic destiffening

“…we can both significantly increase and decrease f G relative to its value for a non-displaced vortex in zero field). We note that frequency downshifting has also been observed in square ferromagnetic elements 35,36 and, to a lesser degree, in triangular elements 37 when moving the core towards a flat edge within the element.…”

Spin waves and domain wall modes in curved magnetic nanowires

“…The mode in the monodomain structure is distributed over the whole wire while the mode in the other magnetization pattern is located at the vortex core. Both modes can have small dependence on the field [12,46]. We draw no conclusion on the nature of mode F and focus on modes D and E in the following.…”

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

“…Additionally, the triangular dot with a magnetic vortex has been confirmed to have wide tunability with the external field [25,26]. Moreover, well-defined magnetic vortex excitation in square elements has been obtained by measuring the induction voltage while applying an external field along the edge [11,27]. To broaden our understanding, we applied a sensitive electrical measurement approach with the separation between the excitation and detection circuits that enables the neglect of complex analysis and the access to dynamics under high power excitation [28].…”