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We present the first surface spin-wave (SW) dispersion measurements up to the surface Brillouin zone boundary of a two monolayer Fe film on W(110) by using spin-polarized electron energy loss spectroscopy. Pronounced features of SW peaks are observed in the spectra at room temperature. We found that the SW energies in the Fe film are strongly reduced compared to spin waves in bulk Fe and to theoretical predictions. Our results suggest that this reduction is caused by the reduction of exchange interaction within the 2 ML Fe on W(110) as compared to bulk Fe.

The high lateral resolution of spin-polarized scanning tunneling microscopy allows new insights into the spin structure of antiferromagnets on the nanometer range. We demonstrate the capability to image a well-defined in-plane component of the sample spin polarization and discuss the spin structure of antiferromagnetic bct Mn in contact with the ferromagnetic Fe(001) substrate. Mn atoms couple ferromagnetically within a Mn atomic plane, while normal to the surface a layer-wise antiferromagnetic order was found. Magnetic frustrations arise in this system at Fe substrate steps at the interface, where topologically induced 180 degrees domain walls are created in the Mn film. A clear widening of the enforced domain walls with increasing Mn thickness was found. The measured widths could be fitted with a linear function and are explained on the basis of a Heisenberg model., ((c) 2005 Wiley-Liss, Inc.)

We have grown Fe films on an epitaxial Pd monolayer on Cu(001) single crystals at room temperature, both Fe and Pd by pulsed laser deposition. The presence of the Pd interlayer influences growth, structure, and magnetism of the Fe films. Up to the thickness of 1.6 ML the Fe films show an out-of-plane easy axis of magnetization which changes to in-plane above. A linear dependence of the longitudinal Kerr rotation on the Fe thickness is obtained despite existing structural transformations. A strong increase of the Curie temperature TC is observed for the Fe films on Pd/Cu(001) compared to the Fe films grown directly on Cu(001). A correlation of the magnetic properties with possible structural changes and the role of Pd monolayer is discussed. [ABSTRACT FROM AUTHOR]

Photoelectron emission microscopy is combined with soft x-ray magnetic circular dichroism (XMCD) absorption spectroscopy to obtain local element-resolved quantitative magnetic properties with microscopic resolution. This is applied to study 0–14 ML Fe wedges with a slope of 0.055 ML/μm on 6 ML Co/Cu(001). Local XMCD spectra at the Fe L[sub 2,3] edge confirm the presence of three magnetically different thickness regions of Fe with effective spin moments of 2.5μ[sub B] (0–4.5 ML), 0.7μ[sub B] (4.5–11 ML), and 1.8μ[sub B] (>11 ML). The value of 0.7μ[sub B] in the second phase is consistent with an fcc Fe phase containing nonferromagnetic layers underneath a ferromagnetic surface. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on Fe films grown on Au-buffered Si(001) showing perpendicular magnetization at ambient temperatures. The in-plane magnetization in ultra-thin Fe films grown at 150 K reorients irreversibly out-of-plane as a result of annealing close to room temperature. A Au cap layer which is expected to segregate to the top of the Fe film may be responsible for this behaviour. This hypothesis is based on the observation of an in-plane to out-of-plane reorientation of magnetization upon the growth of an ultra-thin Au cap layer on a slightly thicker Fe film. The origin of such a strong out-of-plane anisotropy of Fe induced by Au is discussed. [ABSTRACT FROM AUTHOR]

Selective adsorption of Fe deposited on the organic molecule 3,4,9,10-perylene-tetracarboxylic-3, 4,9,10-dianhydride (PTCDA) is used to prepare a self assembled magnetic nanostripe structure on a vicinal Ag surface. Scanning tunneling microscopy reveals that after PTCDA deposition on the Ag(10 8 7) surface a grating-like domain pattern is formed. It consists of alternating stripes of molecule-covered facets and uncovered (111) terraces. Fe adsorption takes place selectively on the molecule-covered stripes forming disk-shaped super-paramagnetic islands with a polar easy magnetization axis. [ABSTRACT FROM AUTHOR]

Studies the morphology, structure and magnetism of iron (Fe) films thermally deposited on stepped copper (Cu)(111) by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and magneto-optical Kerr effect (MOKE). Magnetism in reduced dimensions; Information on MOKE measurements.

Elastic and magnetic properties of ultrathin iron films on tungsten (110) are investigated. In situ film stress measurements during growth show stress values of 25 GPa per deposited monolayer. Our experiments indicate that the tremendous film stress triggers the formation of a misfit dislocation network at a coverage of 1.5 monolayers. The effect of the film stress and its spatial variation on the magnetic behavior are discussed. We find a high coercivity of order 0.3 T for 1.5 monolayer thick films. A model is presented that explains the high coercivity in terms of strong domain wall pinning. [ABSTRACT FROM PUBLISHER]

The magnetism of sesquilayer bcc iron films on W(110) is investigated. Coercivity data and theoretical calculations indicate that the freezing of the magnetization at low temperatures reflects exchange-dominated domain-wall pinning rather than superparamagnetic spin-glass behaviour. [ABSTRACT FROM PUBLISHER]

Presents images of the magnetic domains of iron(100) surfaces using energy-resolved photoemission microscopy. Forms of magnetic dichroism in direct photoemission and secondary electron emission; Uses of the angular dependencies of the magnetodichroic effect; Applications of the magnetic spectromicroscopy based on the magnetodichroic phenomena.

Focuses on the behavior of unoccupied exchange split bands in iron on approaching the Curie temperature at different points in the Brillouin zone. Analysis of the minority and majority states near the H point in body-centered cubic iron.

The growth and the morphology of ultrathin Fe50Mn50 alloy films, deposited by thermal co-evaporation of Fe and Mn on Cu(0 0 1) at room temperature are studied by scanning tunneling microscopy (STM). A high density of small islands of single and double atomic height is nucleated during the initial stages of growth of Fe50Mn50 on Cu(0 0 1). The film growth proceeds further in a nearly perfect layer-by-layer mode. Topographic STM images corresponding to Fe50Mn50 film thicknesses above 10 atomic monolayers reveal atomically flat terraces with islands or holes of monoatomic height (≈0.18 nm). In addition, a fine structure with an apparent corrugation height of about 0.05 nm is recognized. Scanning tunneling spectroscopy measurements prove the spectroscopic origin of this corrugation. It is attributed to local concentration differences of the constituents of the chemically disordered Fe50Mn50 alloy. [Copyright &y& Elsevier]

The idea of investigating large wave-vector magnetic excitations in ultrathin films by spin-polarized electron spectroscopy is briefly reviewed. The historical background of the paper is based on the personal experience of the authors who collaborated and discussed with Douglas Mills regarding this subject. Douglas Mills' impact on the understanding of fundamental mechanisms involved in the excitation process and the development of the theory of magnetic excitations is outlined. In addition, the temperature effects on the large wave-vector magnetic excitations in ultrathin Fe films are addressed. The experimental results of magnon excitations in the pseudomorphic Fe monolayer on W(110) are presented. The temperature dependence of the magnon dispersion relation is discussed. [ABSTRACT FROM AUTHOR]

We provide direct experimental evidence which demonstrates that, in the presence of a large spin-orbit coupling, the lifetime, amplitude, group, and phase velocity of the magnons propagating along two opposite (but crystallographically equivalent) directions perpendicular to the magnetization are different. A real time and space representation reveals that magnons with the same energy (eigenfrequency) propagate differently along two opposite directions. Our findings can inspire ideas for designing new spintronic devices. [ABSTRACT FROM AUTHOR]

Abstract: A contribution originating from the Co/Pd and Fe/Pd interfaces to the magneto-optical Kerr effect (MOKE) rotation is analyzed for Co and/or Fe films grown on a Pd-buffer-monolayer on Cu(001). A clear increase of the MOKE signal in comparison to the Co(Fe) films grown directly on Cu(001) is detected. An interpretation is supported by similar observations for Co films grown on Pd(110) and Pd(001). In particular, the sign reversal of the Kerr loops with increasing thickness of the Co(Fe) films is discussed. Magneto-optical effects are separated from the real magnetization and its dependence on the film thickness. [Copyright &y& Elsevier]

Spin-polarized electron energy loss spectroscopy (SPEELS) is a unique tool to determine the spin-wave dispersion of ultrathin films and surfaces over the whole Brillouin zone. Ultrathin Co films on Cu(001) show well-defined spin-wave loss peaks in the SPEEL spectra. For 3 ML Fe films on 1 ML Co/Cu(001) the spin-wave peaks are much broader compared to the Co case but show dispersion. In 5-ML-thick bcc Fe films on W(110), a very broad feature assigned to spin-wave excitation was observed as well, which, however, does not show significant dispersion in the investigated range of large wavevectors. [Copyright &y& Elsevier]

Single-crystalline Fe/MgO/Fe magneto-tunnel junctions were grown epitaxially on GaAs(0 0 1). Independent magnetization switching was achieved by pinning the magnetization of one of the Fe electrodes by antiferromagnetic coupling via Cr to another Fe layer (GaAs/Fe/Cr/Fe/MgO/Fe). For the antiparallel magnetization orientation in the Fe/Cr/Fe trilayer, “reversed” minor hysteresis loops are measured with longitudinal MOKE. The shape of the loop corresponding to the top “free-Fe” electrode is determined by four-fold magnetic anisotropy with the easy-axis along [1 0 0], superimposed by a weak uniaxial anisotropy with [0 1 0] easy-axis. The loops are asymmetric due to a delicate balance between the uniaxial anisotropy and magnetic interlayer coupling between the Fe electrodes separated with a thin MgO spacer. [Copyright &y& Elsevier]

We report on the out-of-plane magnetization in Fe/Ni and Fe/Au bilayers grown on GaAs(0 0 1). For Ni thicknesses of several monolayers, the magnetization of the Fe/Ni bilayer increases linearly with the Fe film thickness, which is typically observed when Fe grows in the BCC-structure. For thicknesses up to 8 ML, Ni is nonmagnetic such as in the Fe/Ni/GaAs(0 0 1) structure. This could be due diffusion of Ga. Up to thickness of 2 ML the Fe overlayer is magnetized out-of-plane, however at low temperatures only. The nature of the out-of-plane spin orientation is discussed, also in view of the crystallographic structure of the Fe/Ni bilayer and by comparison with the Fe/Au bilayer grown on GaAs(0 0 1). [Copyright &y& Elsevier]

We report on the magnetic and structural characterization of Au/(Ni)Fe/MgO/Fe magneto-tunnel junctions grown on InP(0 0 1) and GaAs(0 0 1). On GaAs substrates almost perfect single crystal junctions with sharp interfaces were achieved as seen by low energy electron diffraction and transmission electron microscopy. In situ magnetization loops obtained with the longitudinal magneto-optic Kerr effect show an independent switching of magnetization of both Fe layers suggesting that the two Fe layers are magnetically decoupled by the MgO layer. [Copyright &y& Elsevier]