Radio frequency magneto-impedance effect in spin tunneling junctions

The effect of radio frequency magneto-impedance in spin tunneling jucntions Co/Al-oxide/Co fabricated on glass substrate was investigated by ion-beam sputtering. The junction impadence was measured by using the voltages of two cobalt electrodes and a standard resistor at room temperature over a frequency range of 0.1-100 MHz. It was observed that the magneto-impadence ratio exhibited a positive value at frequencies less than the roll-off frequency and a negative value at frequencies higher than the roll-off frequency. It was also observed that the imaginary part of the magneto-impedance ratio was positive throuout the frequency region measured and approached zero at high frequencies.