Incident Power Influence on Magnetoimpedance Element With Domain-Wall Resonance

We investigated the influence of the incident power on thin-film magnetoimpedance (MI) elements. When the incident power is relatively low, the impedance profile shows a typical frequency dependence, which can be explained by the theory based on the skin effect, eddy current loss, and ferromagnetic resonance. On the other hand, with the increase of the incident power, the impedance profiles show another impedance peak and large inductance decrease owing to domain-wall resonance (DWR) at a lower frequency. The peak height and inductance at 1 MHz increase with the applied field, and the resonant frequency shifts to a higher frequency. The impedance changes related to DWR strongly depend on the incident power. The field at which the impedance has a maximum value shifts to a lower field with the increase of the incident power. The dependence of the impedance peak values on the field reveals an optimal incident power to achieve a higher sensitivity for field detection. The obtained results indicate that the DWR enhances the sensitivity of thin-film MI elements at a relatively lower frequency, compared with the case without DWR; an incident power of approximately -10 dBm at 30 MHz was optimal in this paper.