Microwave Oscillations of the Giant Magnetoresistive Element in a Magnetic Field Perpendicular to the Plane

Applied voltage and magnetic field dependence of microwave oscillations have been studied for the giant magnetoresistive (GMR) element. In this experiment, a magnetic field is applied perpendicular to the plane of GMR films. It is found that the power spectral density (PSD) is less dependent on the direction of magnetic field and the resistance gap induced by the magnetic field corresponds to the rapid increase of PSD. Moreover, noise peaks are observed in a high frequency range (about 8 GHz or higher) when a magnetic field of more than 2000 Oe is applied. The peak frequencies shift to higher frequency as the magnitude of magnetic field increases. In contrast to a magnetic field, the peak frequencies and their widths are more susceptible to the direction of current.