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MA: Fachverband Magnetismus

MA 46: Magnetic Measurement Methods

MA 46.4: Vortrag

Donnerstag, 10. März 2016, 16:15–16:30, H33

Study of Magnetic Vortex Oscillations in Permalloy Disks by Lorentz TEM and Differential Phase Contrast Microscopy — •Johannes Wild, Michael Vogel, Michael Mueller, Christian Back, and Josef Zweck — Institute of Experimental and Applied Physics, University of Regensburg

In a cylindrical nanodisk with a thickness of a few ten nanometers the magnetic ground state is a vortex. The magnetization curls in the plane of the disk either in clockwise or counterclockwise circulation and points out of the plane at the center. The center is called vortex core and there the magnetization can point either up or down.

We structured Permalloy (Ni₈₀Fe₂₀) disks on SiN₃ membranes and investigated them in the transmission electron microscope (TEM) while applying an AC spin-polarized current. The quantitative in-plane induction of the disks is imaged in Lorentz TEM mode and with differential phase contrast microscopy (DPC). To our knowledge we show the first DPC measurements of oscillating vortices.

We investigated the behavior of the vortex core oscillation on the applied frequencies and the temperature dependence of the resonance frequency.