Exploration of magnetization reversal and coercivity of epitaxial NiO {111}/NiFe films

Abstract

Magnetic and crystallographic properties of molecular beam epitaxially grown Fe3O4/NiO superlattices and Fe3O4 filmsWe have grown epitaxial NiO ͕111͖ films of thicknesses ranging from 60 to 1200 Å, deposited 45 Å NiFe films on these NiO substrates, and made measurements of exchange field and coercivity, of the effective uniaxial anisotropy, of rotational hysteresis, and of the training effect on these films. We find that the large coercive fields, ϳ500 Oe, observed in these epitaxial systems can be understood using a model in which the magnetization reversal process is by rotation, with the coercive field determined by the effective uniaxial anisotropy of the system. This effective anisotropy is in turn determined by the anisotropy of the NiO and depends on NiO thickness.

Temperature and set field dependence of exchange bias training effects in Co/NiO/[Co/Pt] heterostructures with orthogonal easy axes

“…The training effect in exchange bias-like systems is dominated by the dynamics of the AFM interfacial layer, in particular by the deviation of the surface magnetization from equilibrium due to thermal activation [2,3,11,14,15,27,[33][34][35][36][37]. The non-stationary exchange bias indicates a NiO interface magnetization that deviates from its equilibrium configuration, with a slow return 5.…”

Microwave permeability study for antiferromagnet thickness dependence on exchange bias field in NiFe/lrMn layers

“…Exchange bias field appears for a thicker AF layer namely 32 Å , reaches 68 Oe for a 45 Å thick IrMn layer and then sligthly decreases. This behavior has been observed in many AF/F systems [10,20] and has been predicted theoretically [8,21]). H p0 and H e +H c curves are perfectly similar within the experimental uncertainties.This effect has been previously observed in IrMn/F systems [22] and predicted theoretically [13].…”

“…Fig. 2 versus IrMn thickness curves are typical of many exchange bias systems [8,19]. H c exhibits a broad peak response for 25 Å ot AF o 60 Å .…”

“…In particular, many studies were focused on the variations of H e versus the AF or F thickness [8,9]. They are usually based on the hysteresis loop measurements and interpretations [10,11].…”

Size Dependence of Structures and Properties of Magnetic Materials

“…[293]) and H e and T B are sizedependent, which is emphasized in this section. Besides, H e and T B are also functions of AFM orientation (compensated versus uncompensated AFM surface [298][299][300][301][302][303] and in-plane versus out-of-plane AFM spins [298,299,302]), of FM/AFM interface disorder (roughness [299,301,302,[304][305][306], crystallinity [307,308], grain size [309,310], of interface impurity layers [311]), and of strain effect [312][313][314], of stoichiometry [293] or of presence of multiple phases [315] and so forth.…”