Current-induced microwave spectra were measured in small-sized giant magnetoresistance devices composed of a NiFe vortex free layer and an out-of-plane magnetized Co/Pd multilayer polarizer. The influence of a large direct current (DC) and a bias field on the excited mode of the free layer is systematically investigated. For small current values, microwave spectra due to the vortex core oscillation were observed around 1 GHz, while the frequency abruptly changed to 4-4.5 GHz at certain DC values. The experimental data were reproduced by micromagnetic simulation, which indicates that the mode change of the vortex core oscillation in the free layer is dominated by the Oersted field from the large DC.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)