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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]

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]

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]

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]

This overview summarizes important aspects of the cantilever stress measurement technique and its application to measurements of adsorbate-induced surface stress changes and magnetization-induced magnetoelastic stress (also called magnetostrictive stress) of ferromagnetic monolayers. The application of the cantilever technique as a torque magnetometer with monolayer sensitivity is demonstrated. The stress measurements indicate a correlation between surface stress changes and surface reconstruction, and they also identify the often decisive role of the magnetoelastic anisotropy for the non-bulklike magnetic anisotropy of ferromagnetic monolayers. [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]

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]

We have fabricated Co atomic chains and nanowires on a Pd(110) surface oriented along the [1-10] direction. This is possible due to high diffusion anisotropy of the Co adatom on the Pd(110) surface. The Co nanowires on Pd(110) exhibit a strong uniaxial in-plane magnetic anisotropy, in which the easy axis is along [1-10], i.e., nanowire direction. [ABSTRACT FROM AUTHOR]

Magnetization configuration in Fe/Rh/Fe0.5Co0.5/Rh(001) can be non-orthogonal due to competition between the anisotropy and the exchange coupling. Soft x-ray resonant magnetic reflectivity allows us to probe the magnetic profile along the growth axis with in-plane and perpendicular magnetization components. By using different modes of acquisition, we show that it is possible to determine separately the magnetic profile of both magnetization components. Measurements at the Co L3-edge enable us to investigate the magnetism of the alloy layer independently from the layer of Fe. [ABSTRACT FROM AUTHOR]

Magnetic anisotropy depends strongly on the density of states at the Fermi level. If significant contributions to magnetocrystalline anisotropy energy (MAE) are due to spin-polarized quantum well states (QWS), a significant increase of MAE can occur periodically as a function of film thickness. The oscillation period L is determined by the wavelength of the corresponding electron waves. The uniaxial magnetic anisotropy of fcc-Co is found to oscillate with a period of 2.3 ML. In contrast, in bcc-Fe, the uniaxial magnetic anisotropy oscillates with a period of 5.9 ML. We attribute such oscillations to QWS in a minority-spin d-band at the Fermi level. [ABSTRACT FROM AUTHOR]

Analyzes the consequences of the thickness dependence of anisotropy in ultrathin films for the spin-reorientation transitions (SRT) behavior in applied field for the two major field configurations. Occurrence of spontaneous SRT; Specification to ultrathin films.

Presents a study which investigated the magnetic anisotropy of Iron (Fe) or nickel (Ni) ultrathin films. Methodology of the study; Experimental results; Theoretical interpretation; Conclusions.

Presents the abstract of the study 'Magnetic Properties of MBE Structures Using fcc Co/Cu(001) and bcc Fe/Cu(001),' by B. Heinrich, Z. Celinski, K. Myrtle, J.F. Cochran, M. Kowalewski, A.S. Arrott and J. Kirschner.

The continuum theory of micromagnetism is used to study ultrathin films with magnetic anisotropy varying laterally on the nanometer scale. A series of infinitely long stripes with alternating in- and out-of-plane uniaxial anisotropy is considered as a model for patterned ferromagnetic films. The analytical solution based on an effective anisotropy description of the dipolar energy is given as a function of the material parameters (exchange and anisotropy constants) and the width of the stripes. States of uniform and non-uniform magnetization are obtained. For film of finite thickness the exact value of the dipolar energy is calculated numerically and the numerical solution is compared with the analytical one. We find that the correction to the dipolar energy is negligible for nickel, while for cobalt and iron it has to be considered as a function of the anisotropies, the width of the stripes and the thickness of the film. [Copyright &y& Elsevier]

The effect of orthogonal exchange coupling between antiferromagnetic CoO and ferromagnetic Ni/Pd(001) on the perpendicular anisotropy of Ni films is studied. The thickness range in which Ni films show a perpendicular easy magnetization axis is extended by growing CoO on top of them, however, only at temperatures below TN of CoO. The perpendicular orientation of Ni spins and the in-plane orientation of CoO spins are confirmed by the magneto-optic Kerr effect/x-ray magnetic circular dichroism and x-ray magnetic linear dichroism, respectively. Additionally, a perpendicular exchange bias shows up at low temperature. [ABSTRACT FROM AUTHOR]

Using surface x-ray diffraction in combination with ab initio calculations we have studied the atomic structure of ultra-thin ZnO films deposited on Fe(l 10). In contrast to expectation that ZnO adopts the "graphitic" hexagonal Boron-nitride structure to the Wurtzite (WZ) structure is observed. Its formation is related to oxygen impurities in Fe(110) hollow sites inducing an anisotropic charge redistribution within the film which is characterized by a metallic surface. Our results provide a deeper understanding of depolarization mechanisms in ultrathin polar films at the atomic scale. [ABSTRACT FROM AUTHOR]

The effect of quantum well states (QWS) formed in a Cu overlayer on the magnetic anisotropy of Fe and of Co films underneath is investigated at low temperatures. An oscillatory magnetic anisotropy is observed below 50K, with a period of LCu = 5.8 ML, and it is the same for Cu/Fe and Cu/Co. We attribute this effect to QWS from sp electrons in Cu which hybridize to d electrons al the Fermi level in Fe (and Co) and thus modify the magnetic anisotropy at low temperatures. This is why the effect was not so pronounced in the experiments reported 15 years ago showing the low-amplitude oscillations detected at 170 K [Ch. Würsch et al., Nature (London) 389, 937 (1997)]. [ABSTRACT FROM AUTHOR]

The effect of quantum well states on the magnetic anisotropy of Co films grown on vicinal Cu(001) substrates was studied by in situ magneto-optic Kerr effect in a temperature range of 5 K to 365 K. The uniaxial magnetic anisotropy is found to oscillate as a function of Co thickness with a period of 2.3 atomic layers, modulated exactly as theoretically predicted by L. Szunyogh et al. [Phys. Rev. B 56, 14036 (1997)] and independently by M. Cinal [J. Phys. Condens. Matter 15, 29 (2003)] and M. Cinal and A. Umerski [Phys. Rev. B 73, 184423 (2006)]. Sub-monolayer Au coverage was used to fine-tune magnetic anisotropy and to provide convenient experimental access to anisotropy oscillations. The anisotropy oscillations, which are present up to room temperature, are attributed to quantum well states in the minority d band at the Fermi level of Co. [ABSTRACT FROM AUTHOR]

Abstract: So-called split hysteresis loops have been measured for ultrathin ferromagnetic films grown on stepped surfaces. Since the shape of the loops is sensitive to the direction in which the magnetic field is applied with respect to the steps, the sample orientation against the field is particularly important. We performed systematic magneto-optical Kerr effect studies for 15 and 58ML of Fe grown on Au(1,1,13). In view of the complex magnetic anisotropy of such systems we discuss representative hysteresis loops taken at sample orientations misaligned from the field (and laser beam) direction. In particular, the presence of a so-called low field component to the hysteresis loops is discussed and its reversed polarity is explained. [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]