Double Hysteresis Loop and Loop Asymmetry in Perpendicularly Exchange-Biased Pt/Co/Pt/IrMn Thin Films

Abstract

Double hysteresis loops and asymmetric reversals were observed for perpendicularly magnetized and exchange-biased Pt/Co/Pt/IrMn thin films in the magneto-optic Kerr effect and the Hall effect measurements. Drastic changes in double hysteresis loop and loop asymmetry were found in the magnetization reversal process of the Pt/Co/Pt/IrMn structures with the increase of antiferromagnet layer thickness. The applied external magnetic field angle was varied from easy axis to hard axis of magnetization, where changes in the asymmetry of hysteresis loops were observed. Reasons for the double hysteresis loops and asymmetric loops were discussed. The results of this study emphasize the importance of the antiferromagnetic film thickness and the applied magnetic field angle for the exchange-biased bilayers.