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Fe/MgO/Fe single-crystalline magnetotunneling structures were epitaxially grown on GaAs(001). An independent magnetization switching in the Fe electrodes was achieved by pinning the magnetization of the Fe-top electrode by antiferromagnetic coupling across a Cr spacer to another Fe film. Such Fe/Cr/Fe/MgO/Fe/GaAs(001) structures exhibit in-plane anisotropy, which ensures a discrete switching behavior of magnetization simplifying the shape of the hysteresis loop. The field dependence of magnetization was measured along the [110] and [100] crystallographic directions of GaAs(001) substrate and modeled by minimizing the total magnetic energy of the system. A peculiar magneto-optical behavior (similar to a reversed hysteresis loop) is explained by magneto-optical phase angles, which are determined mainly by the optical properties of the semiconducting GaAs substrate. [ABSTRACT FROM AUTHOR]

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]

Thermal deposition (TD) and pulsed laser deposition (PLD) techniques were used to prepare GaAs/Fe(001) crystalline ultrathin films. The magnetic environment of Fe at the Fe/GaAs(001) interface was investigated by means of conversion electron Mössbauer spectroscopy using an 57Fe probe layer having the equivalent thickness of two atomic layers. The magnetic anisotropies were measured using ferromagnetic resonance. PLD samples were affected by an appreciably higher degree of interface alloying compared with the TD films. The interface in-plane fourfold (cubic) anisotropy is significantly increased and the in-plane interface uniaxial anisotropy is significantly decreased in the PLD samples compared to those prepared using TD. The effective perpendicular demagnetizing field in the PLD films is significantly decreased compared to the TD samples due to an unexpected increase in the interface uniaxial perpendicular anisotropy at the Fe/Au(001) interface. [ABSTRACT FROM AUTHOR]

The magnetization states of 20-nm-thick rectangular Co thin-film elements are studied with micromagnetic modeling and x-ray magnetic circular dichroism photoemission electron microscopy. The energies of ten domain configurations obtained in the modeling are compared with the frequency of occurrence of the corresponding virgin domain structures as a function of aspect ratio from 1:1 to 1:3 and of width from 200 to 600 nm. The results show that the abundance of the virgin states is largely determined by the magnetic energy densities of the elements. [ABSTRACT FROM AUTHOR]

We show that for some ultrathin multilayer structures the proportionality of the longitudinal Kerr ellipticity signal to the magnetic film thickness does not take place. Instead, thinner magnetic layers give even twice larger contributions than the thicker ones located a few monolayers deeper. This effect is demonstrated both experimentally and theoretically on ultrathin Fe/Cr/Fe sandwich systems prepared on GaAs(001) surfaces. Such a behavior is explained by a depth variation of phase relations between the optically reflected wave and the wave generated by the magneto-optical interaction. This mechanism becomes very effective close to the phase where the magneto-optical ellipticity cancels. [ABSTRACT FROM AUTHOR]

We have performed magnetic domain imaging with spatial, temporal, and layer resolution using x-ray photoelectron emission microscopy. The element selectivity of x-ray magnetic circular dichroism allows the magnetization dynamics of the different magnetic layers in spin-valve-like FeNi/Cu/Co trilayers to be studied separately, using the time structure of synchrotron radiation. The unique possibilities of this technique have been used to study the influence of the intrinsic magnetic properties of the different layers on the magnetization dynamics and the interlayer magnetic coupling. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We demonstrate, that spin-polarized electron energy loss spectroscopy is a unique tool to determine spin-wave dispersion curves of ultrathin films and surfaces over the whole Brillouin zone. For ultrathin Co films on Cu(001) the excitation of a spin wave appears as a well defined peak in the loss spectrum. 3 ML Fe films on 1 ML Co/Cu(001) films show spin-wave excitation peaks as well though much broader compared to the Co case. The spin-wave energy at the surface zone boundary of about 140 meV for the Fe film is nearly a factor of 2 smaller than that of the Co films. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Fe/Cr/Fe trilayers were epitaxially grown on atomically flat GaAs(001). For the thickness of Cr spacer layer corresponding to antiferromagnetic coupling, “reversed” minor hysteresis loops were measured with longitudinal magneto-optical Kerr effect (MOKE), i.e., a negative “magnetization” signal was detected when the thicker bottom Fe layer was saturated along the applied field. This behavior is interpreted by depth variations of the MOKE sensitivity. Magnetization reversal shows that both antiferromagnetic switching and spin–flop transition fields depend on the ratio of both Fe film thicknesses. The shape of the MOKE loops becomes more complex with further deposition of MgO and Fe layers on the top of the Fe/Cr/F/GaAs(001) stack. Superconducting quantum interference device measurements confirm the interpretation of the MOKE loops and demonstrate homogeneity and sharpness of the interfaces in the structures. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which demonstrated high-resolution imaging of domains and domain walls in the scanning electron microscope. Imaging of surface domains and domain walls; Discussion of stoner excitations in itinerant ferromagnets; Examination of spin-polarized photoemission from thin films.

Studies the diffusion of Fe, Co and Ni from a dot deposited onto a W(110) substrate. Analysis of spread directions for all three metals to <100>; Influence of step directions on the substrate surface; Inducing of spreading anisotropy by the cap layer; Formation of a structure during the spreading process.

Tetragonal distortion in Fe0.5Co0.5 alloy films grown epitaxially on Rh(001) substrates results in an easy magnetization axis perpendicular to the film plane up to the thickness of 17 ML. The distortion is supported by a Rh-overlayer; thus the strong perpendicular anisotropy can be kept when another Fe0.5Co0.5 film is grown on top of the Rh/Fe0.5Co0.5/Rh(001) structure. Depending on the thickness of the Rh spacer, the top and bottom Fe0.5Co0.5 films are either ferro- or antiferromagnetically coupled. The net magnetization of the antiferromagnetically coupled Fe0.5Co0.5/Rh/Fe0.5Co0.5 bilayer switches at the field which depends on the difference between magnetizations of both the Fe0.5Co0.5 layers. The final covering of the Fe0.5Co0.5/Rh/Fe0.5Co0.5/Rh(001) structure with Rh increases the switching field. The effect is explained by a locally enhanced magnetization in the Rh/Fe1-xCox interfaces. [ABSTRACT FROM AUTHOR]

In tetragonally distorted Fe0.5Co0.5 alloy films grown epitaxially on Pd(001), Ir(001), and Rh(001) substrates the crystal field locates the electronic states near the Fermi level (EF) with one being below EF and the other above EF with an energy separation smaller than in bulk nondistorted material. This results in a strong uniaxial anisotropy and an easy magnetization axis perpendicular to the film plane up to the thickness up to which the films remain tetragonally distorted. The strongest perpendicular anisotropy is achieved when the Fe0.5Co0.5 films are grown on Rh(001) (c/a=1.24); it systematically decreases for Ir(001) (c/a=1.18) and Pd(001) (c/a=1.13) substrates. The phenomenon can be understood as a result of an increasing uniaxial anisotropy with an increasing c/a ratio up to the maximum at c/a=1.24 for which the maximum uniaxial magnetic anisotropy has been theoretically predicted. [ABSTRACT FROM AUTHOR]

Fe/MgO/Fe/Cr/Fe tunneling structures were epitaxially grown directly on GaAs(001) without buffer layer. Interdiffusion in the Fe/GaAs interface was investigated using conversion electron Mössbauer spectroscopy. An independent magnetization switching in the Fe electrodes was achieved by pinning the magnetization of the Fe-top electrode by antiferromagnetic coupling across a Cr spacer to another Fe film. For transport measurements, optical lithography and ion etching were applied to reduce the junction area. A tunneling magnetoresistance of 10%–12% at room temperature was found. [ABSTRACT FROM AUTHOR]

The 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. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have studied the magnetic states of self-organized Fe islands on W(001) by means of spin-polarized scanning tunneling spectroscopy (Sp-STS). Single-domain and vortex states in the nanoscale islands have been observed. The high-resolution magnetic images enable to experimentally determine the boundary between the single-domain and vortex states. The single-domain state was always found below a thickness of 6 nm and a diameter of 120 nm in Fe islands. The boundary directly observed with Sp-STS is consistent with theoretical predictions. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Magnetization as a function of temperature calculated with Monte Carlo techniques is compared to experimental results of Fe stripes grown on vicinal Cu(111) surfaces. The stripes are step decorations grown with molecular beam epitaxy (MBE), are 1-2 monolayers thick, and display perpendicular magnetization. The atomic parameters are determined from fully relativistic electronic structure calculations. The moments are found to be 2.57&micron;[sub B], with some variation due to film thickness, and uniaxial anisotropy of 40 &micron;Ry/atom for Fe atoms facing vacuum. The Heisenberg model extended to include crystalline anisotropy as well as dipole-dipole interactions is considered for two different values of the exchange constant: J=20 and 2 meV. Under a large applied field (4000 G), the calculated saturation magnetization falls slowly from 507 emu/cm[sup 3] with an increase in temperature until it falls rapidly around 600 K, after which a more modest falloff with an increase in temperature is observed. For larger d the rapid change occurs for higher temperatures. The importance of disorder in the height and width of the stripes is investigated by generating stripe geometries with a model that incorporates nucleation and growth of Fe particles at step edges under the constraint of constant deposition from MBE. The primary effect of disorder in the stripes is to reduce the saturated magnetization at lower temperatures. [ABSTRACT FROM AUTHOR]

The electron transport and magnetoresistance (MR) were investigated in high quality crystalline epitaxial Fe(001) and Au(001) films and exchange coupled Au/Fe/Au/Fe/GaAs(001) trilayer structures. Fits to the experimental data were based on the semiclassical Boltzmann equation, which incorporates the electronic properties obtained from first-principles local density functional calculations. The fits require a surprisingly high asymmetry for the spin dependent electron lifetimes in Fe, τ[sup ↓]/τ[sup ↑]=10 at room temperature. Despite the large atomic terraces at the Au/vacuum and Fe/GaAs interfaces the scattering at the outer interfaces was found to be diffuse. The origin of MR in Au/Fe/Au/Fe/GaAs(001) structures is due to electron channeling in the Au spacer layer. The measured MR is consistent with the diffusivity parameters s[sup ↑]=0.55, s[sup ↓]=0.77 at the metal-metal interfaces. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The giant magnetoresistance of crystalline Fe/Cu/Fe(001) epitaxial structures characterized by scanning tunneling microscopy are presented. Fe/Cu/Fe(001) trilayers capped with Au are grown directly on GaAs(001) using a new procedure for producing pure Fe layers with As-free Fe surfaces on GaAs(001). The temperature dependence of the magnetoconductance and sheet resistance measured from 4 to 300 K is modeled by the Boltzmann equation assuming that the mean free paths in the crystalline epitaxial layers are equal to those in bulk materials. The results of the simple model suggest that the coefficient of the specular scattering at the Fe/GaAs interface is R=0.45, while the scattering at the outer Au interface is diffuse. Spin asymmetry scattering at the metallic interfaces is ΔT=|T[sup ↑]-T[sup ↓]|=0.34, T[sup avg]=(T[sup ↑]+T[sup ↓])/2=0.79. The sheet resistance was best modeled using a low temperature mean free path of 25 nm in the Fe layer. © 2000 American Institute of Physics. [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]

The correlation between mechanical stress and magnetic anisotropy of Ni and Fe films on Cu(001) is investigated. The magnetoelastic coupling and the film stress during the growth are measured in situ with a highly sensitive optical bending beam technique. For Ni a dramatically reduced magnetoelastic coupling of B[sub 1]=3.5 MJ/m[sup 3] is found for films thinner than 10 ML, roughly one third of the bulk value of 9.4 MJ/m3. This change is explained by a strain correction to the magnetoelastic coupling. The influence of the interfaces does not significantly contribute to the magnetoelastic coupling. A very small magnetoelastic coupling of 0.4 MJ/m3 for Fe films in the range from 12 ML to 25 nm is attributed mainly to the crystallographic orientation of the bcc–Fe. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present static measurements of the domain structure and dynamic results on domain wall motion and local susceptibility obtained by spin-polarized scanning tunneling microscopy. The topography and the magnetic structure of the sample are recorded simultaneously with down to 10 nm resolution. With this technique, domain wall movement on Co(0001) is studied in situ. In some cases, the magnetization of the sample is locally influenced by the stray field of the tip. Measuring higher harmonics in the tunneling current allows one to quantify this influence and measure magnetic susceptibilities on similar scales. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Localized electrochemical deposition of small Co clusters on Au (111) has been achieved by using the tip of a scanning tunneling microscope (STM) as an electrochemical nanoelectrode. In contrast to most of the reported techniques to create nanostructures, this approach avoids irreversible modifications of both substrate and deposit during the preparation process. A special polarization routine of the STM tip allows a purely electrochemical growth of Co clusters with diameters as small as 15 nm. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated magnetic circular dichroism in valence band photoemission (MCDAD) from 15 monolayer thick face-centered cubic nickel (Ni) films on copper. Illustration of a series of intensity spectra for different photon energies; Discussion on the relativistic band structure of Ni along the change axis; Demonstration of MCDAD.

Deals with a study which performed magnetic dichroism measurements of the valence bands of films of fcc Co/Cu (001) using angle-resolved ultraviolet photoemission in low-symmetry, off-normal emission geometries and linearly polarized light. Evidence of both spin-dependent surface transmission and magnetic dichroism in the angular distribution of photoelectrons.

Presents information on the study conducted which assessed the electronic and magnetic properties of normally immiscible FeCu(100) alloy films. Measurements of the magnetic circular dichroism in soft x-ray absorption of these fcc FeCu alloy films; Behavior of the magnetic moments of the Fe films; Experimental procedures used in the study; Results of the study.

We describe a new "complete" spin-polarized electron energy loss spectrometer comprising a spin-polarized primary electron source, an imaging electron analyzer, and a spin analyzer of the "spin-polarizing mirror" type. Unlike previous instruments, we have a high momentum resolution of less than 0.04 Å-1, at an energy resolution of 90-130 meV. Unlike all previous studies which reported rather broad featureless data in both energy and angle dependence, we find richly structured spectra depending sensitively on small changes of the primary energy, the kinetic energy after scattering, and of the angle of incidence. The key factor is the momentum resolution. [ABSTRACT FROM AUTHOR]

We have designed and constructed a spin polarized low energy electron diffraction system working in the reflected electron pulse counting mode. This system is capable of measuring asymmetries due to spin-orbit and exchange interactions. Photoemission from a strained GaAs/GaAsP super lattice is used as the source of spin polarized electrons. Spin-orbit asymmetry is evaluated for Ir(100) single crystal at various energies. Subsequently, exchange asymmetry has been evaluated on 40 monolayer Fe deposited on Ir(100). This instrument proves to be useful in understanding structure and magnetism at surfaces. [ABSTRACT FROM AUTHOR]

An in situ stress measurement setup using an optical 2-beam curvature technique is described which is compatible with the stringent growth conditions of pulsed laser deposition (PLD) of perovskite oxides, which involves high substrate temperatures of 1000 K and oxygen partial pressures of up to 1 × 10-4 millibars. The stress measurements are complemented by medium energy electron diffraction (MEED), Auger electron spectroscopy, and additional growth rate monitoring by a quartz microbalance. A shielded filament is used to allow for simultaneous stress and MEED measurements at high substrate temperatures. A computer-controlled mirror scans an excimer laser beam over a stationary PLD target. This avoids mechanical noise originating from rotating PLD targets, and the setup does not suffer from limited lifetime issues of ultra high vacuum (UHV) rotary feedthroughs. [ABSTRACT FROM AUTHOR]

Here, we present the first systematic study on the temperature dependence of the extension of the superconducting proximity effect in a 1-2 atomic layer thin metallic film, surrounding a superconducting Pb island. Scanning tunneling microscopy/spectroscopy (STM/STS) measurements reveal the spatial variation of the local density of state on the film from 0.38 up to 1.8 K. In this temperature range the superconductivity of the island is almost unaffected and shows a constant gap of a 1.20 ± 0.03 meV. Using a superconducting Nb-tip a constant value of the proximity length of 17 ± 3 nm at 0.38 and 1.8 K is found. In contrast, experiments with a normal conductive W-tip indicate an apparent decrease of the proximity length with increasing temperature. This result is ascribed to the thermal broadening of the occupation of states of the tip, and it does not reflect an intrinsic temperature dependence of the proximity length. Our tunneling spectroscopy experiments shed fresh light on the fundamental issue of the temperature dependence of the proximity effect for atomic monolayers, where the intrinsic temperature dependence of the proximity effect is comparably weak. [ABSTRACT FROM AUTHOR]

We report on the design of an ion source for the production of single and double charged Helium ions with kinetic energies in the range from 300 eV down to 5 eV. The construction is based on a commercial sputter ion gun equipped with a Wien-filter for mass/charge separation. Retardation of the ions from the ionizer potential (2 keV) takes place completely within the lens system of the sputter gun, without modification of original parts. For 15 eV He+ ions, the design allows for beam currents up to 30 nA, limited by the space charge repulsion in the beam. For He2+ operation, we obtain a beam current of 320 pA at 30 eV, and 46 pA at 5 eV beam energy, respectively. In addition, operating parameters can be optimized for a significant contribution of metastable He*+ (2s) ions. [ABSTRACT FROM AUTHOR]

The time stability of a polarization analyzer that is used for imaging of magnetic structures in a scanning electron microscope with spin polarization analysis (spin-SEM or SEMPA) is investigated. The detector is based on the diffraction of low-energy electrons at a W(100) crystal at 104.5 eV (LEED detector). Due to the adsorption of hydrogen from residual gas, a change of the scattering conditions is found that causes an angular shift of the LEED beams as well as changes of intensity. The quality factor, which describes the efficiency of the detector in SEMPA application, however, is found to be almost constant up to a hydrogen coverage of θ ≈ 0.25. This gives stable working conditions within roughly 1 h at vacuum conditions of 10-10 mbar. [ABSTRACT FROM AUTHOR]

We report on a compact electron spin analyzer based on exchange scattering from a magnetic surface. The heart of the detector is an Fe(001) thin film grown on W(001) with chemisorbed oxygen in the p(1×1) structure. The device is mounted at the exit of an energy dispersive analyzer and works at a scattering energy of about 13.5 eV. Its figure of merit is 2×10-3, combined with an excellent stability of more than 2 weeks in UHV. [ABSTRACT FROM AUTHOR]

In this article, a novel time-of-flight spectrometer for two-electron-emission (e,2e/γ,2e) correlation spectroscopy from surfaces at low electron energies is presented. The spectrometer consists of electron optics that collect emitted electrons over a solid angle of approximately 1 sr and focus them onto a multichannel plate using a reflection technique. The flight time of an electron with kinetic energy of Ekin≃25 eV is around 100 ns. The corresponding time- and energy resolution are typically ≈1 ns and ≈0.65 eV, respectively. The first (e,2e) data obtained with the present setup from a LiF film are presented. [ABSTRACT FROM AUTHOR]

We demonstrate the use of a novel design of a photoelectron microscope in combination to an imaging energy filter for momentum resolved photoelectron detection. Together with a time resolved imaging detector, it is possible to combine spatial, momentum, energy, and time resolution of photoelectrons within the same instrument. The time resolution of this type of energy analyzer can be reduced to below 100 ps. The complete ARUPS pattern of a Cu(111) sample excited with He I, is imaged in parallel and energy resolved up to the photoelectron emission horizon. Excited with a mercury light source (hν=4.9 eV), the Shockley surface state at the energy threshold is clearly imaged in k-space. Electron-electron interactions are observed in momentum space as a correlation hole in two-electron photoemission. With the high transmission and the time resolution of this instrument, possible new measurements are discussed: Time and polarization resolved ARUPS measurements, probing change of bandstructure due to chemical reaction, growth of films, or phase transitions, e.g., melting or martensitic transformations. [ABSTRACT FROM AUTHOR]

By making use of advanced methods for the calculation of electron trajectories in the presence of space charge fields we have designed and built a novel electron energy-loss spectrometer for the purpose of measuring spin flip excitations at surfaces. The measurement of the spin asymmetry requires a deflection angle between the photocathode and the sample position which amounts to 90° in total. That deflection angle is not provided by standard electron deflectors, or by a combination of those. We show that a 90° deflection angle can be realized by a combination of two novel deflectors with 90° and 180° deflection angles each. The performance of the new spectrometer matches the performance of the best electron spectrometers developed for surface vibration spectroscopy. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We 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. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A highly efficient time-of-flight electron spectrometer is described. An incident electron current of the order of 10[sup -14] A makes it suitable for studying secondary emission from dielectric surfaces. A microchannel plate position-sensitive detector allows flight distance correction while keeping a large acceptance angle. Measured energy distribution curves of secondary electrons generated from a LiF film by 19-31 eV incident electrons demonstrate good energy resolution and reveal reproducible and stable emission features at 2.6±0.3 eV, 7.2±0.3 eV, and 10.3±0.3 eV. [ABSTRACT FROM AUTHOR]

We report on experimental advances in scanning electron microscopy with polarization analysis that allow the observation of ferromagnetic domains in external magnetic fields of about 0.1 T. This is achieved by using a modified electron optics that produces a magnetic field at the sample surface that is spatially confined on the length scale of 0.1 mm. During imaging, primary and secondary electrons pass through the magnetic field without significant disturbance. We demonstrate that the primary electron beam may be used to keep track of the generated magnetic field. As an exemplary application, the switching processes of rectangular Permalloy elements are analyzed. [ABSTRACT FROM AUTHOR]

We describe the design, construction, and operation of an ion beam assisted deposition source for molecular beam epitaxy in ultrahigh vacuum. At a typical deposition rate of a monolayer per minute, the source may be operated in each of five modes: using self-ions from the vapor, self-ion plus noble gas ions from an additional gas inlet, both pulsed or continuous, or with complete suppression of ions. The source is based on electron bombardment heating of a metal rod or a crucible while the ions generated from the vapor are focused electrostatically onto the sample. Additional ions may be extracted from a noble gas stream injected into the ionization region. Examples for each of the different modes are given for Co deposition onto Cu(111), a system known to resist layer-by-layer growth. [ABSTRACT FROM AUTHOR]

A cantilever magnetometer is described that measures the magnetic moment of ferromagnetic films with submonolayer sensitivity. The magnetometer is incorporated into an ultrahigh vacuum chamber for sample preparation and in situ magnetometry. Standard size single crystals of 5 mm diameter and 2 mm thickness can be used, which are mounted on thin sheet metal. This composite sampleholder works as a cantilever when the bending is induced by the torque exerted by an external magnetic field on a monolayer ferromagnetic film deposited onto the single crystal substrate. We demonstrate the submonolayer sensitivity on Fe monolayers on Cu(100) in the thickness range from 2 to 68 monolayers. The sample holder is designed for internal calibration by passing a current through it and exploiting the well-known current induced magnetic moment. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The scenario of the magnetization reorientation in second-order perpendicular anisotropy approximation is theoretically studied by means of Monte-Carlo simulations. The microstructure is investigated as a function of the difference between first-order anisotropy and demagnetizing energy K[sub eff]=K[sub 1]-E[sub D] and the second-order anisotropy K[sub 2]. An influence of the second-order perpendicular anisotropy on the spin reorientation transition is found when K[sub eff] vanishes. The broadening and coalescing of domain walls found earlier for K[sub 2]=0 is prevented by positive K[sub 2]. The domain wall width and energy are determined by K[sub 2]. For K[sub 2]>0 the transition via a canted vortex-like structure is found which yields the smooth, continuous connection between the vertical domain structure and the vortex structure with in-plane magnetization. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Discusses the design and construction of a combination of a scanning tunneling microscope (STM) and a scanning electron microscope which is working under ultrahigh vacuum (UHV) conditions. Design concept and its realization; Description of the UHV chamber system; Influence of the electron beam on the STM measurement.

Focuses on a electrochemical cell design which enables in situ tunneling microscopy (STM), cyclic voltammetry and optical measurements in a single setup and at the same surface area of the substrate. Overview on the cell design; Measurements and performance.

Develops an electrochemical cell for in situ x-ray diffraction under ultrapure conditions. Cell design; Reduction of oxygen level in the electrolyte by continuous nitrogen flow; Measurement of the electrode potential.

Describes a video-low-energy electron-diffraction (LEED) data. Components and configuration; Data acquisition and processing; Intensity profile mode; Intensity versus energy mode; Asymmetry versus energy mode; Intensity versus time mode; Performance.

We report on an imaging spin-filter for electrons. The specular reflection of low-energy electrons at the surface of a tungsten single crystal is used to project a spin-filtered two-dimensional image onto a position sensitive detector. Spin-filtering is based on the spin-dependent reflectivity of electrons due to spin-orbit coupling in the scattering target, while a two-dimensional field of view, encoded in the angle of incidence, is conserved in the outgoing beam. We characterize the efficiency of the spin-filter by recording photoelectron emission microscopy images of the magnetic domain structure of 8 monolayers cobalt grown on copper (100). [ABSTRACT FROM AUTHOR]

We propose a conclusive characterization of the magnetic configuration of tips for spin-polarized scanning tunneling microscopy studies. We show that both careful tip preparation and characterization by tunneling spectroscopy need to be augmented by in-field measurements to ensure a reliable analysis of a magnetic contrast in spin-polarized scanning tunneling microscopy studies. [ABSTRACT FROM AUTHOR]