Effect of Slit Patterning Perpendicular to Magnetic Easy Axis in Thin Film Inductors

In the case of spiral inductors using magnetic thin films with uniaxial anisotropy, magnetic flux pass through both easy and hard axes in the films. Frequency characteristics of inductance in the spiral inductors strongly depend on magnetization behaviors in the magnetic easy-axis direction. Slit patterning perpendicular to the magnetic easy axis in the magnetic thin films influences domain-wall displacement in the easy-axis direction, raising its resonant frequency and improving the permeability in the MHz range. The permeability at 1 MHz in the easy-axis direction takes the maximum value when the wire width is 0.5 mm in the slit-patterned CoZrTa films. Furthermore, also in composite spiral-inductor devices using the slit-patterned CoZrTa films and ferrite substrates, the inductance at 1 MHz takes the maximum value at the same wire width. The slit patterning perpendicular to the magnetic easy axis is effective to achieve high inductance in the MHz range for magnetic thin-film spiral inductors.