Influence of frequency and DC bias on magneto-impedance behaviors in double-MgO magnetic tunnel junctions

Magneto-impedance (MI) of a double-barrier MgO magnetic tunnel junction (DMTJ) is measured as a function of frequency (20 Hz–3 MHz) and DC bias (−1 to 1 V) under magnetic parallel and antiparallel states. A strong nonlinear effect is observed at all frequencies and the MI changes from positive to negative at the relaxation frequency ∼1/RC. A frequency–dc bias (f–Vf–V) “phase diagram” is mapped out to describe the combination effects of the magneto-impedance response. The decay of the tunnel magneto-resistance (TMR) and tunnel magneto-capacitance (TMC) at high voltage is sufficiently reduced by the double-MgO barrier. The V1 / 2 (the voltage that magnetic response drops to 1/2 of its maximum) of TMC reaches an average value of ∼1.35 V, which is larger than the V1 / 2 of TMR ∼0.95 V, suggesting that the response of TMC is more stable than TMR for high frequency application.