Effect of Granular Spacer on the Exchange Bias Effect in FeMn-Based Film Structures

Abstract

The article deals with a study of interactions between permalloy layers separated by granular Со‒Al₂O₃ spacer. Multilayer Ta/FeNi/FeMn/FeNi/Co–Al₂O₃/FeNi/Ta films prepared by magnetron sputtering are the test object. The spacer thickness and content of metallic phase in the spacer have been varied from 0 to 8 nm and 0 to 40%, respectively. A correlation has been found between the Co concentration in the spacer and critical spacer thickness. When the thickness of the spacer exceeds a critical value, the independent magnetization reversal of the permalloy layers adjacent the spacer takes place. It has been shown that, in the case of both cooperative and independent magnetization reversal of permalloy layers, the presence of a spacer substantially affects the hysteretic properties of film structure. The data obtained can be useful when purposefully controlling the coercive force and exchange-bias field in film structures with the unidirectional anisotropy.