| Summary: | 碩士 === 國立政治大學 === 應用物理研究所 === 103 === We report experimental detection of the behaviors of magnetic vortex cores using out-of-plane (electro)-magnetic fields that oscillates at the eigenfrequencies of novel permalloy magnetic disk structures.
First, We study interlayer-coupled magnetic vortex core and different stable excitation states in resonant perpendicular magnetic field of permalloy(Py)/Cu/Py trilayer disks. The samples are Ta(10)/Py(10)/Cu(3)/Py(25) (thickness in nm) disks of 2μm diameter, patterned via electron-beam lithography. When the samples are located in the gap of ground-signal-ground (GSG) coplanar waveguide, a high-frequency out-of-plane magnetic field (H_r ) is generated by a radio frequency signal generator. When the samples are located on the signal line of the GSG waveguide, in-plane resonant fields (H_t) is applied transversely. We show that by using a sequence of H_t and H_r, different ferromagnetic (FM) layer resonant states can be controlled in a systematic way. We observed several peaks between 5 GHz and 7 GHz, which were sensitive to the field.
Secondly, we study the vortex core excitation of out-of-plane precession motion accompanied with in-plane precession induced by shape anisotropy in resonant perpendicular magnetic field of two-magnetic-disk structures. The samples are Py(10)/Py(40) disks of 1μm/2μm diameter, patterned via electron-beam lithography. We show that by using a sequence of H_t and H_r, the vortex core is excited into in-plane precession motion after out-of-plane precession in resonant perpendicular magnetic. We observed a peaks near 7 GHz, which were different from different position and out-of-plane resonant field intensity.
Lastly, we created skyrmion state by micromagnetic simulation using an in-plane frequency conversion (0Ghz~50GHz) in perpendicular magnetic anisotropy (PMA) materials. In the future, we can use Giant Magnetoresistance (GMR) in spin valve structures to detect the formation of skyrmions experimentally.
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