1,720,984 research outputs found
Local exchange bias observed by photoemission microscopy
No full textBy using a photoemission electron microscope in combination with X-ray magnetic circular dichroism, the domain configuration in a single crystalline Co film exchange coupled to an Fe50Mn50 film is obtained. The effect of the ferromagnetic/antiferromagnetic interaction is observed to be different in Co domains with different magnetization direction, establishing the fact that the exchange bias' is locally set by the magnetization of the ferromagnetic layer, without external field
Magnetic dichroisms in absorption and photoemission for magnetic characterization in x-ray photoelectron emission microscopy
No full textMagnetic contrast for the operation of a photoelectron emission microscope (PEEM) with synchrotron radiation is provided by magnetic dichroisms. Besides the most frequently employed magnetic dichroism, magnetic circular dichroism in x-ray absorption spectroscopy, energy filtering of photoemitted electrons allows one to also use magnetic dichroisms in photoelectron emission as complementary contrast mechanisms. We demonstrate that it is possible to obtain magnetic contrast in photoemission using PEEM equipped with a simple retarding field electron energy analyzer. Magnetic domain images of an ultrathin film of 10 atomic monolayers of Fe on W(001), obtained by three, different contrast mechanisms (circular magnetic dichroism in x-ray absorption, circular magnetic dichroism in Fe valence band photoemission, and linear magnetic dichroism in Fe 3p photoemission) are presented and compared
Influence of exchange bias coupling on the single-crystalline FeMn ultrathin film
No full textPolarization dependent x-ray photoemission electron microscopy was used to investigate the influence of the exchange bias coupling on the disordered ultrathin single-crystalline fcc Fe(50)Mn(50). We find that the critical thickness of the FeMn film, where the antiferromagnetic (AF) order is formed, varies with changing the magnetization direction of the ferromagnetic (FM) layer from out-of-plane to in-plane. Surface magneto-optical Kerr effect measurements (SMOKE) further manifest the shift of the critical thickness with alternating the exchange bias coupling. It indicates that the spin structure of the FeMn layer near the FM layer is modified by the presence of exchange bias coupling and the properties of the coupling. Our results provide direct experimental evidence that the AF spin structure at the interface between the FM and AF layers is strongly influenced by the exchange bias coupling
Microspectroscopic two-dimensional Fermi surface mapping using a photoelectron emission microscope
No full textWe demonstrate the use of a photoelectron emission microscope in connection with a retarding field electron energy analyzer for the fast acquisition of two-dimensional momentum resolved photoelectron angular distribution patterns. This opens the possibility to combine spatial, momentum, and energy resolution of photoelectrons within the same instrument. We have applied this to observe the Cu(001) Fermi surface from a selected region of the sample. A well defined bulk Fermi surface is quickly mapped in this way
Tuning the magnetic coupling across ultrathin antiferromagnetic films by controlling atomic-scale roughness
No full textCharacterization and control of the interface structure and morphology at the atomic level is an important issue in understanding the magnetic interaction between an antiferromagnetic material and an adjacent ferromagnet in detail, because the atomic spins in an antiferromagnet change direction on the length scale of nearest atomic distances. Despite its technological importance for the development of advanced magnetic data-storage devices and extensive studies, the details of the magnetic interface coupling between antiferromagnets and ferromagnets have remained concealed. Here we present the results of magneto-optical Kerr-effect measurements and layer-resolved spectro-microscopic magnetic domain imaging of single-crystalline ferromagnet - antiferromagnet ferromagnet trilayers. Atomic-level control of the interface morphology is achieved by systematically varying the thicknesses of the bottom ferromagnetic and the antiferromagnetic layer. We find that the magnetic coupling across the interface is mediated by step edges of single-atom height, whereas atomically. at areas do not contribute
Magnetic domain investigation in Co/Cu/FeMn trilayers
No full textThe magnetic domain patterns of epitaxial single-crystalline Co/FeMn bilayers and Co/Cu/FeMn trilayers were investigated by magnetic circular dichroism domain imaging using photoelectron emission microscopy. The as-grown domain size increases continuously with increasing Cu layer thickness, which is attributed to the decrease of the interlayer exchange coupling between ferromagnetic Co and antiferromagnetic FeMn layers. Domain images of the Co layer acquired after applying different external magnetic fields show a decrease in coercivity with increasing Cu layer thickness, confirming the reduction of magnetic coupling energy with increasing Cu thickness
Layer-resolved imaging of magnetic interlayer coupling by domain-wall stray fields
No full textLayer-resolved magnetic domain images of epitaxially grown Co/Cu/Ni trilayers on Cu(001) have been studied, taken by photoelectron emission microscopy using x-ray magnetic circular dichroism as a magnetic contrast mechanism. In these trilayers the Ni layers are magnetized perpendicularly to the film plane, whereas the Co magnetization is in the film plane. Comparison of the as-grown magnetic domain images of the Co and Ni layers reveals the influence of the magnetostatic stray fields from Ni domain walls on the Co domain pattern as a lateral displacement of the Co domain wall position compared to the Ni domain walls. The effect is quantified by comparing to the effect of external magnetic fields, and is found to be equivalent to about 250 Oe. Micromagnetic simulations using the Landau-Lifshitz-Gilbert equation confirm that size of the Ni domain wall stray field interaction
Exchange coupling between ferro- and antiferromagnetic layers across a non-magnetic interlayer: Co/Cu/FeMn on Cu(001)
No full textThe as-grown magnetic domain patterns of epitaxial single-crystalline Co/FeMn bilayers and Co/Cu/FeMn trilayers were investigated by magnetic circular dichroism domain imaging using a photoelectron emission microscope. Small domains were observed when Co was deposited directly on top of antiferromagnetic FeMn films. On inserting a Cu spacer layer between the ferromagnetic Co layer and the antiferromagnetic FeMn layer, the as-grown domain size increases continuously with increasing Cu layer thickness, which is attributed to the decrease of the interlayer exchange coupling between the Co and FeMn layers. Domain images of the Co layer acquired after applying different external magnetic fields confirm the relation between as-grown domain size and interface coupling to the antiferromagnetic FeMn layer across the nonmagnetic Cu spacer layer. It is found that a field of 44 Oe is sufficient to annihilate most small domains in the area where Co and FeMn are coupled through the Cu wedge, while it has no effect on the domain configuration of a Co/FeMn bilayer. By analysing the dependence of the average domain size of the Co layer on the Cu thickness in terms of interface coupling between the Co and FeMn layers across the Cu layer, the apparent estimated coupling energy was found to be different for different Co thickness. This is ascribed to kinetic barriers hindering the formation of larger domains from smaller ones
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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