Magnetocapacitance effect of spin tunneling junctions

Magnetocapacitance effect of coercive differential spin tunneling junctions Co(100Å)/Al ₂O ₃(∼20Å)/Co(500Å) fabricated onto a glass substrate by ion-beam mask sputtering was investigated. The impedance was measured by a four-probe method at room temperature in the frequency range from 120 Hz to 1 MHz. It is found that the effective capacitance changes with the application of an external magnetic field. At high frequencies, the magnetocapacitance ratio is as large as the dc magnetoresistance ratio. However, at low frequencies, capacitance changes cannot be observed because the measurement sensitivity is too low. The magnetocapacitance effect was hence found to be a promising tool for high frequency magnetic sensing.