Domain processes in the magnetization reversal of exchange-biased IrMn/CoFe bilayers

Abstract

Defect mediated tuning of exchange bias in IrMn/CoFe nanostructure

Angular dependence of magnetization reversal process in exchange coupled ferromagnetic/antiferromagnetic bilayers

“…Due to the presence of the unidirectional anisotropy, the domain wall formation in the FM layer could be different for the decreasing and increasing field branches of the hysteresis loop. 5,11,12,14 This difference can cause the asymmetric shape of the hysteresis loop. Therefore, the domain wall formation in both the FM and AF layers may be the main reason for the persistence of the coercivity H C and the asymmetric shape of the M t ϪH loops in the NiFe/NiO system even when the field is applied close to the hard axis.…”

Concentric 360° domain wall nesting in magnetic tunnel junction films: a Lorentz TEM study

“…In particular, the formation of 360° domain walls (DWs) has been reported for MTJ [9][10][11] and related exchange bias systems [12][13][14][15][16] and is known to disrupt uniform switching, leading to noise and stability issues during device operation. Conceptually, these 360° DWs arise from the coalescence of two of the more common 180° Néel DWs that separate regions of opposite magnetisation [17,18], often because the first 180° DW becomes pinned by a structural defect.…”

Erase/restorable asymmetric magnetization reversal in polycrystalline ferromagnetic films

“…14,15 The asymmetric hysteresis behaviour has been investigated by using various techniques, such as domain imaging, 1,2 polarized neutron reflectometry, 16,17 magnetoresistance, 18 Kerr magnetometry, 19 etc. Different mechanisms have been proposed including higher order FM anisotropy, 4,17 dispersion of the FM or AFM anisotropy axes, 2,3 or training effect induced irreversibility, 22,23 however, a detailed understanding of this effect is still lacking. Nevertheless, a generally accepted origin that induces such asymmetry is an exchange induced unidirectional anisotropy which breaks symmetry of magnetization reversal.…”

“…The use of the two sets of coils allows one to investigate both the longitudinal and transverse magnetization curves, as is often done with Kerr magnetometer. 3,5,14 Longitudinal in-plane hysteresis loop measurement in various applied field directions indicates that the plated film has uniaxial anisotropy. Figures 1(a) and 1(b) display hysteresis loops measured from 1 lm thick film in the induced easy (h ¼ 0 ) and hard (h ¼ 90 ) axes.…”

“…This is mainly due to the potential novel applications in magneticstorage and sensor technology, but also due to an interest in the complex magnetization reversal process itself. An important magnetization reversal property of magnetic thin films is the unusual reversal caused by complex anisotropy, such as asymmetric magnetization reversal, [1][2][3][4] multi-stepped switching, [5][6][7][8][9][10][11][12][13] etc. The asymmetric hysteresis loops are mainly observed in exchange-biased ferromagnetic-antiferromagnetic (FM/AFM) systems [14][15][16][17][18][19] and in other exchange system like exchange spring coupled bilayers.…”