Asymmetric exchange bias in NiFe/FeMn/NiFe multilayer films

Ultrawideband microwave noise filter: Hybrid antiferromagnet/ferromagnet exchange-coupled multilayers

“…Due to the overlap of several hysteresis loops with different exchange bias fields, the hysteresis loop manifests itself as a multiple-stage reversal. Similar behavior has previously been observed 16,17 for the exchange biased system using FeMn, where it was claimed that the bottom interface normally has a better unidirectional anisotropy constant and the reason for that is that the top interface is rougher than the bottom interface. 16 For the case of FeCo-MnIr multilayers since J K acting on each interface is identical the loop manifests itself as a single-shifted loop.…”

Permalloy–FeMn exchange-biased multilayers grown on flexible substrates for microwave applications

“…Due to the overlap of several hysteresis loops with different exchange bias fields, the hysteresis loop manifests itself as a multiple-stage reversal. Previously, several groups [11,12] observed similar behavior for the exchange-biased system using FeMn, where they claimed that the bottom interface normally has ARTICLE IN PRESS a better unidirectional anisotropy constant. The reason for this is that the top interface is rougher than the bottom interface [11].…”

“…Previously, several groups [11,12] observed similar behavior for the exchange-biased system using FeMn, where they claimed that the bottom interface normally has ARTICLE IN PRESS a better unidirectional anisotropy constant. The reason for this is that the top interface is rougher than the bottom interface [11]. Another interesting point that should be mentioned is the vertical shift of the hysteresis loop that was similarly observed in several systems [13,14].…”

Bottom and top AF/FM interfaces of NiFe/FeMn/NiFe trilayers

“…For FeMn-based spin valve systems, the NiFe buffer layer is usually used to stabilize the AF g-phase, resulting in NiFe/FeMn/NiFe trilayer-like structure, where the bottom and top NiFe layers are, respectively, called as seed and pinned layers. When the seed and pinned layer thicknesses are different and/or the lower (NiFe/FeMn) and upper (FeMn/ NiFe) interfaces have substantial structural or/and magnetic differences, the spin valve has an asymmetrical M(H) curve with two regions: one related to the lower (NiFe/FeMn) interface and the other associated with the upper (NiFe/FeMn) one, each one with its respective H ex value [15][16][17].…”

“…Nevertheless, it has been reported [18] that the EB main parameters depend on several factors, such as: interfacial spin configuration, interface roughness between the FM and AF materials, textures (structural and magnetic), crystalline grain size and AF layer thickness. For example, Lee et al [17] have studied the NiFe (10 nm)/FeMn (30 nm)/NiFe (10 nm) trilayer by magnetization and transmission electron microscoNiFe (TEM) measurements and they have found that the seed and pinned layers have distinct H ex values due to different roughness values at the lower and upper NiFe/FeMn interfaces.…”