Interaction between exchange-bias systems inNi80Fe20∕Fe50Mn50∕

Chi Wah Leung

¹

,

M. G. Blamire

²

Abstract

The coupling effect between two adjacent exchange bias systems in a trilayer structure was studied. NiFe/ FeMn/ Co trilayers were prepared in a controlled field to induce conventional biasing in the bottom NiFe/ FeMn system, but not in the top FeMn/ Co structure. By comparing the magnetic behavior of asdeposited samples with that after field cooling from high temperature, we probed the interactions between the two biased systems through a common antiferromagnetic spacer. The temperature dependences of exchange bias fields and coercivities indicated that exchange bias was not simply an effect between a ferromagnet and an antiferromagnet across the interface; the bulk of the antiferromagnet layer, together with the presence of the second biasing system, were required to account for the final behavior of the whole trilayer exchange bias structure.

Role of the antiferromagnetic bulk spins in exchange bias

“…Moreover, equivalent CoFe/FeMn interfaces exhibit larger EB in trilayers than in bilayers [29]. A similar result was found in FeNi/FeMn, FeMn/Co bilayers and FeNi/ FeMn/Co trilayers [30]. The differences in the exchange bias field, for equivalent FM/AFM interfaces in bilayers and trilayers, can only be explained considering the bulk AFM spin structure.…”

Exchange bias in FeNi/FeMn/FeNi multilayers

“…Therefore, the suggestion about the existence of magnetic coupling between the FM layers through the AF layer is quite rare [28,29]. In most of the published articles, the authors study the hypothesis of possible interaction or its absence between two exchange bias systems through a common antiferromagnetic spacer [11,13,[21][22][23][30][31][32][33]. Malinowski et al found for FeNi/IrMn/FeNi trilayers that the magnetic coherence of the antiferromagnetic layer at the bottom interface does not extend up to the top, the upper side of the IrMn layer has no chance to get biased from the bottom FeNi layer [11].…”

Role of the Antiferromagnetic Bulk Spin Structure on Exchange Bias

“…Several techniques have been applied to study AF domains [10][11][12], and 90 or 180 domain walls were claimed for different systems [13][14][15][16][17][18][19][20]. Although recent experiments [21,22] suggest that the bulk AF sets the EB, whether EB is purely controlled by the interface or AF bulk is still controversial.…”