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Articles 31 - 45 of 45
Full-Text Articles in Physics
Magnetic Susceptibility Of Nanoscale Kondo Systems, Ralph Skomski, R. Zhang, Parashu Kharel, Axel Enders, Sy_Hwang Liou, D. J. Sellmeyer
Magnetic Susceptibility Of Nanoscale Kondo Systems, Ralph Skomski, R. Zhang, Parashu Kharel, Axel Enders, Sy_Hwang Liou, D. J. Sellmeyer
Axel Enders
The mesoscopic Kondo effect in metallic nanoparticles containing a magnetic impurity is investigated by model calculations. A Maxwell–Garnett approach is used to approximately determine the resistivity of doped nanoparticles in a matrix, and the magnetic susceptibility is estimated from the confinement of the conduction electrons. Conductivity measurements of nanoparticles embedded in a matrix are difficult to realize, because metallic matrices distort the Kondo cloud, whereas insulating or semiconducting matrices yield a very weak signal. By comparison, susceptibility measurements do not suffer from these shortcomings. The Kondo effect survives in nanoparticles even if the cluster size is much smaller than the …
Adsorbate And Thermally Induced Spin Reorientation Transition In Low-Temperature-Grown Fe/Cu(001), D. Peterka, Axel Enders, G. Haas, K. Kern
Adsorbate And Thermally Induced Spin Reorientation Transition In Low-Temperature-Grown Fe/Cu(001), D. Peterka, Axel Enders, G. Haas, K. Kern
Axel Enders
Adsorbate and thermally induced changes of the spin reorientation transition in Fe wedges grown at 140 K on Cu(001) substrates are investigated by the magneto-optical Kerr effect and Kerr microscopy. The adsorption of oxygen causes a complete reorientation of the easy axis of magnetization into the film plane. In contrast to that carbon monoxide decreases the critical thickness for the reorientation transition of the film by 0.7 monolayer down to 3.6 monolayers, while films thinner than 3.6 monolayers remain magnetized perpendicularly. These adsorbate-induced changes can be ascribed to a change in the surface magnetic anisotropy. Also annealing of the films …
The Role Of Interfaces In The Magnetoresistance Of Au/Fe/Au/Fe/Gaas(001), Axel Enders, T. L. Monchesky, Kenneth Myrtle, R. Urban, Brett Heinrich, Jurgen Kirschner, X.-G. Zhang, W. H. Butler
The Role Of Interfaces In The Magnetoresistance Of Au/Fe/Au/Fe/Gaas(001), Axel Enders, T. L. Monchesky, Kenneth Myrtle, R. Urban, Brett Heinrich, Jurgen Kirschner, X.-G. Zhang, W. H. Butler
Axel Enders
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↓/ τ↑ =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 …
Stress Evolution During The Growth Of Ultrathin Layers Of Iron And Iron Silicide On Si(111), D. Sander, Axel Enders, J. Kirschner
Stress Evolution During The Growth Of Ultrathin Layers Of Iron And Iron Silicide On Si(111), D. Sander, Axel Enders, J. Kirschner
Axel Enders
Using a simple optical deflection technique, we measured continuously the mechanical stress during the growth of Fe films of 0.1–1.5 nm thickness on Si(111) in ultrahigh vacuum (UHV). The stress versus coverage dependence is discussed in view of the different growth modes during the various stages of Fe deposition. The deposition of up to 0.3 nm Fe induces a compressive stress of -1 N/m. We assign this stress to the formation of a reactive Fe–Si interface layer with a silicide-like structure. Subsequent Fe deposition at 300 K leads to a small tensile stress of 0.7 N/m, whereas the deposition at …
Self-Assembled Nanometer-Scale Magnetic Networks On Surfaces: Fundamental Interactions And Functional Properties, Carlo Carbone, Sandra Gardonio, Paolo Moras, Samir Lounis, Marcus Heide, Gustav Bihlmayer, Nicolae Atodiresei, Peter Dederichs, Stefan Blügel, Sergio Vlaic, Anne Lehnert, Safia Ouazi, Stefano Rusponi, Harald Brune, Jan Honolka, Axel Enders, Klaus Kern, Sebastian Stepanow, Cornelius Krull, Timofey Balashov, Aitor Mugarza, Pietro Gambardella
Self-Assembled Nanometer-Scale Magnetic Networks On Surfaces: Fundamental Interactions And Functional Properties, Carlo Carbone, Sandra Gardonio, Paolo Moras, Samir Lounis, Marcus Heide, Gustav Bihlmayer, Nicolae Atodiresei, Peter Dederichs, Stefan Blügel, Sergio Vlaic, Anne Lehnert, Safia Ouazi, Stefano Rusponi, Harald Brune, Jan Honolka, Axel Enders, Klaus Kern, Sebastian Stepanow, Cornelius Krull, Timofey Balashov, Aitor Mugarza, Pietro Gambardella
Axel Enders
Nanomagnets of controlled size, organized into regular patterns open new perspectives in the fields of nanoelectronics, spintronics, and quantum computation. Self-assembling processes on various types of substrates allow designing fine-structured architectures and tuning of their magnetic properties. Here, starting from a description of fundamental magnetic interactions at the nanoscale, we review recent experimental approaches to fabricate zero-, one-, and two-dimensional magnetic particle arrays with dimensions reduced to the atomic limit and unprecedented areal density. We describe systems composed of individual magnetic atoms, metal-organic networks, metal wires, and bimetallic particles, as well as strategies to control their magnetic moment, anisotropy, and …
Temperature Dependence Of The Surface Anisotropy Of Fe Ultrathin Films On Cu(001), Axel Enders, D. Peterka, D. Repetto, N. Lin, Ivan Dmitriev, Klaus Kern
Temperature Dependence Of The Surface Anisotropy Of Fe Ultrathin Films On Cu(001), Axel Enders, D. Peterka, D. Repetto, N. Lin, Ivan Dmitriev, Klaus Kern
Axel Enders
We report an experimental approach to separate temperature dependent reversible and irreversible contributions to the perpendicular magnetic anisotropy of Fe films grown at low temperatures on Cu(001) substrates. The surface anisotropy KS(T) is found to decrease linearly with temperature, causing a thermally induced spin reorientation into the plane. The irreversible shift of the spin reorientation transition and the coercivity of the iron films are directly correlated to the increasing Fe island size during annealing. The increased coercivity is discussed in terms of domain wall energy inhomogeneities provided by the islands.
Complex Magnetic Phase In Submonolayer Fe Stripes On Pt(997), Jan Honolka, T. Y. Lee, K. Kuhnke, D. Repetto, V. Sessi, Peter Wahl, A. Buchsbaum, P. Varga, S. Gardonio, C. Carbone, S. R. Krishnakumar, P. Gambardella, M. Komelj, R. Singer, M. Fähnle, K. Fauth, G. Schütz, Axel Enders, K. Kern
Complex Magnetic Phase In Submonolayer Fe Stripes On Pt(997), Jan Honolka, T. Y. Lee, K. Kuhnke, D. Repetto, V. Sessi, Peter Wahl, A. Buchsbaum, P. Varga, S. Gardonio, C. Carbone, S. R. Krishnakumar, P. Gambardella, M. Komelj, R. Singer, M. Fähnle, K. Fauth, G. Schütz, Axel Enders, K. Kern
Axel Enders
Correlations between magnetism and morphology of iron nanostructures of monatomic height on Pt(997) substrates are studied using x-ray magnetic circular dichroism as well as scanning tunneling microscopy and helium scattering. A drastic collapse of the average magnetization by more than a factor of 4 is observed when increasing the iron coverage from 0.1 to 0.2 ML. This effect goes along with a softening of the magnetic anisotropy energy and a gradual reorientation of the magnetic easy axis from in plane to out of plane. The experimental findings together with electronic density-functional calculations suggest the formation of a complex magnetic phase …
Absence Of Local Magnetic Moments In Ru And Rh Impurities And Clusters On Ag(100) And Pt(997), Jan Honolka, K. Kuhnke, L. Vitali, Axel Enders, K. Kern, S. Gardonio, C. Carbone, S. R. Krishnakumar, P. Bencok, S. Stepanow, P. Gambardella
Absence Of Local Magnetic Moments In Ru And Rh Impurities And Clusters On Ag(100) And Pt(997), Jan Honolka, K. Kuhnke, L. Vitali, Axel Enders, K. Kern, S. Gardonio, C. Carbone, S. R. Krishnakumar, P. Bencok, S. Stepanow, P. Gambardella
Axel Enders
The magnetism of quench-condensed Ru and Rh impurities and metal films on Ag(100) and Pt(997) has been studied using x-ray magnetic circular dichroism. In the coverage range between 0.22 and 2.0 ML, no dichroic signal was detected at the M3,2 absorption edges of Ru on Ag(100) at a temperature of 5 K in the presence of an applied magnetic field. The same was found for coverages between 0.12 and 0.5 ML of Rh on Ag(100) and Pt(997). It is concluded that the magnetic moments of single impurities, small clusters of various shape, and monolayers of the 4d metals are below …
Magnetic Surface Nanostructures, Axel Enders, Ralph A. Skomski, Jan Honolka
Magnetic Surface Nanostructures, Axel Enders, Ralph A. Skomski, Jan Honolka
Axel Enders
Recent trends in the emerging field of surface-supported magnetic nanostructures are reviewed. Current strategies for nanostructure synthesis are summarized, followed by a predominantly theoretical description of magnetic phenomena in surface magnetic structures and a review of experimental research in this field. Emphasis is on Fe- or Co-based nanostructures in various low-dimensional geometries, which are studied as model systems to explore the effects of dimensionality, atomic coordination, chemical bonds, alloying and, most importantly, interactions with the supporting substrate on the magnetism. This review also includes a discussion of closely related systems, such as 3d element impurities integrated into organic networks, surface-supported …
Growth, Structure, Electronic, And Magnetic Properties Of Mgo/Fe(001) Bilayers And Fe/Mgo/Fe(001) Trilayers, M. Klaua, D. Ullmann, J. Barthel, W. Wulfhekel, J. Kirschner, R. Urban, Theodore L. Monchesky, Axel Enders, John F. Cochran, Brett Heinrich
Growth, Structure, Electronic, And Magnetic Properties Of Mgo/Fe(001) Bilayers And Fe/Mgo/Fe(001) Trilayers, M. Klaua, D. Ullmann, J. Barthel, W. Wulfhekel, J. Kirschner, R. Urban, Theodore L. Monchesky, Axel Enders, John F. Cochran, Brett Heinrich
Axel Enders
Single-crystal epitaxial MgO thin films were grown directly onto high-quality Fe single crystal and Fe whisker substrates and covered with Fe/Au layers. Reflection high-energy electron diffraction and low-energy electron diffraction patterns and scanning tunneling microscopy images showed that the growth of MgO proceeded pseudomorphically in a nearly layer-by-layer mode up to six monolayers. A misfit dislocation network is formed for MgO layers thicker than six monolayers. The thin MgO films were characterized electrically by scanning tunneling spectroscopy. The tunneling barrier in MgO was found to depend on the MgO layer thickness, starting from 2.5 eV at two monolayer thickness to …
Substrate-Controlled Growth And Magnetism Of Nanosize Fe Clusters On Pt, Ralph Skomski, J. Zhang, V. Sessi, Jan Honolka, K. Kern, Axel Enders
Substrate-Controlled Growth And Magnetism Of Nanosize Fe Clusters On Pt, Ralph Skomski, J. Zhang, V. Sessi, Jan Honolka, K. Kern, Axel Enders
Axel Enders
The growth and magnetism of nanosize Fe clusters on Pt and other metal surfaces are investigated. Fe clusters have been fabricated directly on the substrates by buffer layer assisted growth under ultrahigh vacuum conditions. The mean cluster diameter and the average cluster spacing were controlled by the Fe coverage and the buffer layer thickness. The enhanced magnetic anisotropy of such clusters of diameters between 0.5 and 10 nm with respect to bulk is discussed. Interface anisotropy contributions are compared with direct dipolar cluster-cluster interaction and indirect interactions mediated by the substrate, including preasymptotic ferromagnetic interaction. It is found that this …
Temperature Dependence Of The Magnetism In Fe/Cu(001), Axel Enders, D. Repetto, D. Peterka, K. Kern
Temperature Dependence Of The Magnetism In Fe/Cu(001), Axel Enders, D. Repetto, D. Peterka, K. Kern
Axel Enders
The correlation between morphology and magnetism of ultrathin epitaxial films is investigated by a combined study of variable temperature scanning tunneling microscopy, magneto-optical Kerr effect measurements, and Kerr microscopy under ultrahigh vacuum condition. The magnetization reversal of the films was studied as a function of temperature by imaging the propagation of Bloch domain walls in situ. It is demonstrated on the example of fcc Fe films grown at 120 K on Cu(001) that changes in the morphology of the films during annealing are directly reflected in modified magnetic properties. Competing pinning mechanisms for the domain wall propagation are identified. The …
Polarized Neutron Reflectometry Study Of The Magnetization Reversal Process In Yba2cu3o7 /La2/3ca1/3mno3 Superlattices Grown On Srtio3 Substrates, J. Hoppler, H. Fritzsche, V. K. Malik, J. Stahn, G. P. Cristiani, H.-U. Habermeier, M. Rössle, Jan Honolka, Axel Enders, C. Bernhard
Polarized Neutron Reflectometry Study Of The Magnetization Reversal Process In Yba2cu3o7 /La2/3ca1/3mno3 Superlattices Grown On Srtio3 Substrates, J. Hoppler, H. Fritzsche, V. K. Malik, J. Stahn, G. P. Cristiani, H.-U. Habermeier, M. Rössle, Jan Honolka, Axel Enders, C. Bernhard
Axel Enders
Using polarized neutron reflectometry we investigated the reversal of the magnetization of a high-Tc superconductor/ferromagnet superlattice that consists of eight bilayers of YBa2Cu3O7(25.6 nm) /La2/3Ca1/3MnO3(25.6 nm) grown on a SrTiO3 substrate. The measurements were performed during a magnetization hysteresis loop at 5 K. We obtained evidence that the reversal in the vicinity of the coercive field proceeds via the switching of micrometer-sized magnetic domains that are considerably larger than the typical domains of La2/3Ca1/3MnO3. Furthermore, these large magnetic domains appear to be more strongly correlated along the vertical direction of the superlattice than along the lateral one. We provide evidence …
Dzyaloshinski–Moriya Micromagnetics Of Magnetic Surface Alloys, Ralph Skomski, Jan Honolka, S. Bornermann, H. Ebert, Axel Enders
Dzyaloshinski–Moriya Micromagnetics Of Magnetic Surface Alloys, Ralph Skomski, Jan Honolka, S. Bornermann, H. Ebert, Axel Enders
Axel Enders
The magnetism of magnetic surface alloys such as Fe–Pt on Pt(997) has been investigated by micromagnetic model calculations. A unique feature of some of these systems is that interatomic exchange, magnetocrystalline anisotropy, and Dzyaloshinski–Moriya (DM) interactions are all of comparable magnitude, of the order of 0.5 meV. This leads to an intriguing nanoscale interplay between ordinary magnetization states and noncollinear spin structures. We identify two cases where the latter dominate. First, for sufficiently strong DM interaction, the zero-field spin structures change from uniform to a canted state with an incommensurate wave vector. Second, a similar transition occurs for weak DM …
Proton Transfer In Surface-Stabilized Chiral And Polar Motifs Of Croconic Acid, Axel Enders
Proton Transfer In Surface-Stabilized Chiral And Polar Motifs Of Croconic Acid, Axel Enders
Axel Enders
No abstract provided.