Enhancement and inverse behaviors of magnetoimpedance in a magnetotunneling junction by driving frequency

The magnetoimpedance effect was employed to study magnetotunneling junction (MTJ) with the structure of Ru (5 nm) Cu (10 nm) Ru (5 nm) IrMn (10 nm) CoFeB (4 nm) Al (1.2 nm) -oxideCoFeB (4 nm) Ru (5 nm). A huge change of more than ±17 000% was observed in the imaginary part of the impedance between the magnetically parallel and antiparallel states of the MTJ. The inverse behavior of the magnetoimpedance (MI) loop occurs beyond 21.1 MHz; however, the normal MI at low frequency and the inverse MI at high frequency exhibit the same magnetization reversal as checked by the Kerr effect. The reversal in MI was due to the dominance of magnetocapacitance at high frequency.