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| 3. |
- Gridneva, Lidia, et al.
(författare)
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Experimental investigation of the spin reorientation of Co/Au based magnetic nanodot arrays
- 2008
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121 .- 1550-235X. ; 77:10
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Tidskriftsartikel (refereegranskat)abstract
- (Co/Au) and (Au/ Co/ Au) nanomagnet arrays grown on nanostructured self-organized SiGe templates have been characterized by means of x-ray photoemission electron microscopy, x-ray magnetic circular dichroism, and by extended x-ray absorption spectroscopy using synchrotron radiation. In-plane magnetization is observed at room temperature for practically all Co thicknesses, a stable macroscopic perpendicular magnetic order only at low temperature. The spin reorientation transition in these dot arrays takes place for smaller Co thicknesses over a broader thickness range than in two-dimensional systems. This finding appears to be related with structural relaxation modifications, occurring within the local Co atom environment, which are not necessarily connected with the orbital moment variations. These variations appear in the form of a systematic increase, correlated with the existence of out-of-plane magnetization.
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- Mulders, A. M., et al.
(författare)
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On The Interface Magnetism Of Thin Oxidized Co Films : Orbital And Spin Moments
- 2009
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 21:12, s. 124211-
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Tidskriftsartikel (refereegranskat)abstract
- An x-ray magnetic circular dichroism study of a polycrystalline Co/CoO bilayer is presented. Using both the chemical specificity and surface sensitivity in the core level techniques, we find that uncompensated Co2+ spin moments participate in the remanent ferromagnetic response of the bilayer that has oxygen nearest neighbors. These are likely located at the Co/CoO interface. As intermixing of magnetic species is not present in Co/CoO, it is concluded that the observed interface moments are due to interface roughness. Given their direction, these moments appear to not directly correlate to the exchange bias in these bilayers.
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- Hahlin, A, et al.
(författare)
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Structure and magnetism of ultrathin epitaxial Fe on Ag(100)
- 2006
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121 .- 1550-235X. ; 73:13
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Tidskriftsartikel (refereegranskat)abstract
- We have made in-situ investigations of ultrathin films of Fe grown on a Ag(100) single crystal. This system is known to exhibit a reorientation of the magnetization, dependent on both Fe thickness and temperature. X-ray absorption fine structure has been recorded for samples prepared in-situ, both in the near edge and in the extended x-ray absorption fine structure (EXAFS) region. Using x-ray magnetic circular dichroism we found that Fe films between 2-5 monolayers show an out-of-plane remanent magnetization. For thicker films the magnetization lies in-plane. By applying the magneto-optical sum rules we found an enhancement of the orbital moment (m(l)) for the out-of-plane phase, whereas the spin moment (m(s)) is unchanged. From the Fe L-edge EXAFS, we obtain information on the local crystallographic structure. A strong correlation between the local crystallographic structure and the magnetic properties is found for the Fe/Ag(100) system. Variations in the nearest neighbor distance of similar to 0.15 angstrom are observed when comparing 3 ML and 25 ML films. By comparison to simulations performed with the FEFF 8.10 code, we can identify a bcc structure for 6-25 ML Fe on Ag(100). For the 3 ML Fe film our simulations indicate strong deviations from any structure derived along the Bain path. We conclude that intermixing and distortion are important to describe the structure in this thickness range.
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- Wolska, A., et al.
(författare)
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XANES studies of Mn K and L-3,L-2 edges in the (Ga,Mn) As layers modified by high temperature annealing
- 2008
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Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 114:2, s. 357-366
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Tidskriftsartikel (refereegranskat)abstract
- Ga1-xMnx As is commonly considered as a promising material for microelectronic applications utilizing the electron spin. One of the ways that allow increasing the Curie temperature above room temperature is to produce second phase inclusions. In this paper Gal-,Mn.As samples containing precipitations of ferromagnetic MnAs are under consideration. We focus on the atomic and electronic structure around the Mn atoms relating to the cluster formation. The changes in the electronic structure of the Mn, Ga and As atoms in the (Ga,Mn)As layers after high temperature annealing were determined by X-ray absorption near edge spectroscopy. The experimental spectra were compared with the predictions of ab initio full multiple scattering theory using the FEFF 8.4 code. The nominal concentration of the Mn atoms in the investigated samples was 6% and 8%. We do not observe changes in the electronic structure of Ca and As introduced by the presence of the Mn atoms. We find, in contrast, considerable changes in the electronic structure around the Mn atoms. Moreover, for the first time it was possible to indicate the preferred interstitial positions of the Mn atoms.
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