High-frequency GMI hysteresis effect analysis by first-order reversal curve (FORC) method

Abstract

In this work, we investigate the giant magnetoimpedance (GMI) hysteresis at high-frequency (10 MHz – 1 GHz) of Co-based amorphous magnetic ribbons. The first-order reversal curve (FORC) method was used to analyze their hysteretic behavior present at a low magnetic field (below 7 Oe). Results show that the GMI hysteresis is related to both the system magnetic anisotropy and the current frequency (through the skin depth). The GMI hysteresis gradually decreases upon frequency increase before disappearing, while a clockwise rotation of the FORC distributions is observed. These results are attributed to a heterogeneous magnetic structure in the magnetic ribbon volume. On the other side, while the cut-off frequency depends on the magnetic anisotropy strength, an inverted GMI hysteresis revives for the higher anisotropy ribbon. Above this frequency inversion, FORC results indicate a hardening of the effective switching field as a thicker region is probed. We propose that in this case, the stronger perpendicular anisotropy creates important differences between the superficial and volumetric anisotropy, enough to induce interaction between the two regions of different magnetization directions. This sensitive FORC protocol can be applied for investigating the GMI hysteresis, and thus the complex magnetic structure of several soft magnetic systems.