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Full-Text Articles in Physics
Temperature Dependence Of Metal-Organic Heteroepitaxy, Geoffrey Rojas, Xumin Chen, Donna A. Kunkel, Matthias Bode, Axel Enders
Temperature Dependence Of Metal-Organic Heteroepitaxy, Geoffrey Rojas, Xumin Chen, Donna A. Kunkel, Matthias Bode, Axel Enders
Axel Enders Publications
The nucleation and growth of 2D layers of tetraphenyl porphyrin molecules on Ag(111) are studied with variable-temperature scanning tunneling microscopy. The organic/metal heteroepitaxy occurs by strict analogy to established principles for metal heteroepitaxy. A hierarchy of energy barriers for diffusion on terraces and along edges and around corners of adislands is established. The temperature is key to activating these barriers selectively, thus determining the shape of the organic aggregates, from a fractal shape at lower temperatures to a compact shape at higher temperatures. The energy barriers for the terrace diffusion of porpyrins and the molecule-molecule binding energy were determined to …
Ultrathin Batio3 Templates For Multiferroic Nanostructures, Xumen Chen, Seolun Yang, Ji-Hyun Kim, Hyung-Do Kim, Jae-Sung Kim, Geoffrey Rojas, Ralph Skomski, Haidong Lu, Anand Bhattacharya, Tiffany Santos, Nathan Guisinger, Matthias Bode, Alexei Gruverman, Axel Enders
Ultrathin Batio3 Templates For Multiferroic Nanostructures, Xumen Chen, Seolun Yang, Ji-Hyun Kim, Hyung-Do Kim, Jae-Sung Kim, Geoffrey Rojas, Ralph Skomski, Haidong Lu, Anand Bhattacharya, Tiffany Santos, Nathan Guisinger, Matthias Bode, Alexei Gruverman, Axel Enders
Axel Enders Publications
The structural, electronic and dielectric properties of high-quality ultrathin BaTiO3 films were investigated. The films, which were grown by ozone-assisted molecular beam epitaxy on Nb-doped SrTiO3(001) substrates and have thicknesses as low as 8 unit cells (u.c.) (3.2 nm), are unreconstructed and atomically smooth with large crystalline terraces. A strain-driven transition to three-dimensional (3D) island formation is observed for films of 13 u.c. thickness (5.2 nm). The high structural quality of the surfaces, together with dielectric properties similar to bulk BaTiO3 and dominantly TiO2 surface termination, makes these films suitable templates for the synthesis of …
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 Heinz 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 Heinz 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 Publications
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 …
Length Scales Of Interactions In Magnetic, Dielectric, And Mechanical Nanocomposites, Ralph Skomski, Balamurugan Balamurugan, Eva Schubert, Axel Enders, David J. Sellmyer
Length Scales Of Interactions In Magnetic, Dielectric, And Mechanical Nanocomposites, Ralph Skomski, Balamurugan Balamurugan, Eva Schubert, Axel Enders, David J. Sellmyer
Axel Enders Publications
It is investigated how figures of merits of nanocomposites are affected by structural and interaction length scales, Aside from macroscopic effects without characteristic lengths scales and atomic-scale quantum-mechanical interactions there are nanoscale interactions that reflect a competition between different energy contributions. We consider three systems, namely dielectric media, carbon-black reinforced rubbers and magnetic composites. In all cases, it is relatively easy to determine effective materials constants, which do not involve specific length scales. Nucleation and breakdown phenomena tend to occur on a nanoscale and yield a logarithmic dependence of figures of merit on the macroscopic system size. Essential system-specific differences …
Is The Magnetic Anisotropy Proportional To The Orbital Moment?, Ralph Skomski, Arti Kashyap, Axel Enders
Is The Magnetic Anisotropy Proportional To The Orbital Moment?, Ralph Skomski, Arti Kashyap, Axel Enders
Axel Enders Publications
The relation between orbital moment and magnetic anisotropy is investigated by model calculations, which show that only a part of the spin-orbit coupling contributes to the anisotropy. A large part of the anisotropy energy, about 50% for iron series elements and nearly 100% for rare-earths, is stored in the nonrelativistic part of the Hamiltonian. A feature important for x-ray magnetic circular dichroism is that the orbital moment of heavy atoms rotates with the spin moment, whereas in light atoms, the orbital moment is recreated in each different direction. In the discussion, we consider three examples of current interest in different …
Anisotropy Of Zigzag Chains Of Palladium, P. K. Sahota, Ralph A. Skomski, Axel Enders, David J. Sellmyer, Arti Kashyap
Anisotropy Of Zigzag Chains Of Palladium, P. K. Sahota, Ralph A. Skomski, Axel Enders, David J. Sellmyer, Arti Kashyap
Axel Enders Publications
Ab initio calculations of the biaxial anisotropy of infinite Pd zigzag chains are presented. The simulations were performed with the Vienna Ab-Initio Simulation Package, using a tetragonal unit cell with a supercell approach where the atoms are repeated along the z-direction. The anisotropy is determined from the energies along the three principal directions [001], [100], and [010]. The second-order anisotropy constants K1 and K'1 were extracted by fitting the calculated energy values to the phenomenological energy. The easiest magnetization direction is along the wire axis, whereas the hardest direction is perpendicular to the plane of the …