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4.0
Mar 31, 2021
03/21
by
Frank Freimuth (Borstenei)
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Customized version of https://www.thingiverse.com/thing:2403440 Created with Customizer! https://www.thingiverse.com/apps/customizer/run?thing_id=2403440
Topics: customized, Robotics, stl, thingiverse
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4.0
Jun 30, 2018
06/18
by
Yuriy Mokrousov; Frank Freimuth
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Lecture Notes of the 45th IFF Spring School "Computing Solids - Models, ab initio methods and supercomputing" (Forschungszentrum Juelich, 2014).
Topics: Mesoscale and Nanoscale Physics, Condensed Matter
Source: http://arxiv.org/abs/1407.2847
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6.0
Jun 29, 2018
06/18
by
Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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Using the Kubo linear-response formalism we derive expressions to calculate the heat current generated by magnetization dynamics in magnets with broken inversion symmetry and spin-orbit interaction (SOI). The effect of producing heat currents by magnetization dynamics constitutes the Onsager reciprocal of the thermal spin-orbit torque (TSOT), i.e., the generation of torques on the magnetization due to temperature gradients. We find that the energy current driven by magnetization dynamics...
Topics: Mesoscale and Nanoscale Physics, Condensed Matter
Source: http://arxiv.org/abs/1602.03319
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4.0
Jun 29, 2018
06/18
by
Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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We show that electric currents are induced in inversion asymmetric ferromagnets if the exchange splitting varies in time after excitation by laser pulses. We interpret this phenomenon as the magnetic variant of the inverse Edelstein effect. Based on \textit{ab initio} calculations we determine the size of this effect in Co/Pt(111) and Mn/W(001) magnetic bilayer systems and investigate its dependence on the magnetization direction. The comparison of our theoretical results to experiments...
Topics: Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1611.09758
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Sep 21, 2013
09/13
by
Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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We report on first principles calculations of the anisotropy of the intrinsic spin Hall conductivity (SHC) in nonmagnetic hcp metals and in antiferromagnetic Cr. For most of the metals of this study we find large anisotropies. We derive the general relation between the SHC vector and the direction of spin polarization and discuss its consequences for hcp metals. Especially, it is predicted that for systems where the SHC changes sign due to the anisotropy the spin Hall effect may be tuned such...
Source: http://arxiv.org/abs/1011.2714v2
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3.0
Jun 29, 2018
06/18
by
Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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We study laser-induced torques in bcc Fe, hcp Co and $L1_0$ FePt based on first-principles electronic structure calculations and the Keldysh nonequilibrium formalism. We find that the torques have two contributions, one from the inverse Faraday effect (IFE) and one from the optical spin-transfer torque (OSTT). Depending on the ferromagnet at hand and on the quasiparticle broadening the two contributions may be of similar magnitude or one contribution may dominate over the other. Additionally,...
Topics: Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1608.02656
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5.0
Jun 30, 2018
06/18
by
Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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In collinear magnets lacking inversion symmetry application of electric currents induces torques on the magnetization and conversely magnetization dynamics induces electric currents. The two effects, which both rely on spin-orbit interaction (SOI), are reciprocal to each other and denoted direct spin-orbit torque (SOT) and inverse spin-orbit torque (ISOT), respectively. We derive expressions for SOT and ISOT within the Kubo linear response formalism. We show that expressions suitable for...
Topics: Mesoscale and Nanoscale Physics, Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1406.3866
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3.0
Jun 30, 2018
06/18
by
Guillaume Géranton; Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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Using the linear response formalism for the spin-orbit torque (SOT) we compute from first principles the SOT in a system of two layers of L1$_0$-FePt(001) deposited on an fcc Pt(001) substrate of varying thickness. We find that at room temperature the values of the SOTs that are even and odd with respect to magnetization generally lie in the range of values measured and computed for Co/Pt bilayers. We also observe that the even SOT is much more robust with respect to changing the number of...
Topics: Mesoscale and Nanoscale Physics, Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1409.1767
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Sep 18, 2013
09/13
by
Kunihiko Yamauchi; Frank Freimuth; Stefan Blügel; Silvia Picozzi
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The microscopic origin of the magnetically-driven ferroelectricity in collinear AFM-E orthorhombic manganites is explained by means of first-principles Wannier functions. We show that the polarization is mainly determined by the "asymmetric electron hopping" of orbitally-polarized Mn eg states, implicit in the peculiar in-plane zig-zag spin arrangement in the AFM-E configuration. In ortho-HoMnO3, Wannier function centers are largely displaced with respect to corresponding ionic...
Source: http://arxiv.org/abs/0803.1166v1
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Sep 22, 2013
09/13
by
Jürgen Weischenberg; Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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Using the full-potential linearized augmented plane-wave method within the density functional theory, we compute all contributions to the scattering independent part of the thermoelectric conductivity tensor, namely the intrinsic contribution and the side-jump contribution. For the ferromagnetic materials bcc Fe, hcp Co, fcc Ni and L1_0 ordered alloys FePd and FePt, our investigations of the energy and temperature dependence of the intrinsic and side-jump contributions show that they are both...
Source: http://arxiv.org/abs/1210.8283v2
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5.0
Jun 29, 2018
06/18
by
Jan-Philipp Hanke; Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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We predict from first principles an entirely topological orbital magnetization in the noncoplanar bulk antiferromagnet $\gamma$-FeMn originating in the nontrivial topology of the underlying spin structure, without any reference to spin-orbit interaction. Studying the influence of strain, composition ratio, and spin texture on the topological orbital magnetization and the accompanying topological Hall effect, we promote the scalar spin chirality as key mechanism lifting the orbital degeneracy....
Topics: Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1610.07573
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Jun 27, 2018
06/18
by
Jan-Philipp Hanke; Frank Freimuth; Stefan Blügel; Yuriy Mokrousov
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When using Wannier functions to study the electronic structure of multi-parameter Hamiltonians $H^{(\boldsymbol k,\bf \lambda)}$ carrying a dependence on crystal momentum $\boldsymbol k$ and an additional periodic parameter $\bf\lambda$, one usually constructs several sets of Wannier functions for a set of values of $\bf\lambda$. We present the concept of higher dimensional Wannier functions (HDWFs), which provide a minimal and accurate description of the electronic structure of multi-parameter...
Topics: Condensed Matter, Materials Science
Source: http://arxiv.org/abs/1503.01717
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Sep 21, 2013
09/13
by
Jürgen Weischenberg; Frank Freimuth; Jairo Sinova; Stefan Blügel; Yuriy Mokrousov
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We report on first-principles calculations of the side-jump contribution to the anomalous Hall conductivity (AHC) directly from the electronic structure of a perfect crystal. We implemented our approach for a short-range scattering disorder model within the density functional theory and computed the full scattering-independent AHC in elemental bcc Fe, hcp Co, fcc Ni, and L1o FePd and FePt alloys. The full AHC thus calculated agrees systematically with experiment to a degree unattainable so far,...
Source: http://arxiv.org/abs/1108.5917v1
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Sep 21, 2013
09/13
by
Björn Hardrat; Nengping Wang; Frank Freimuth; Yuriy Mokrousov; Stefan Heinze
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We present an implementation of the ballistic Landauer-B\"uttiker transport scheme in one-dimensional systems based on density functional theory (DFT) calculations within the full-potential linearized augmented plane-wave (FLAPW) method. In order to calculate the conductance within the Green's function method we map the electronic structure from the extended states of the FLAPW calculation to Wannier functions which constitute a minimal localized basis set. Our approach benefits from the...
Source: http://arxiv.org/abs/1204.3002v1
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Sep 20, 2013
09/13
by
Ersoy Sasioglu; Arno Schindlmayr; Christoph Friedrich; Frank Freimuth; Stefan Blügel
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We present a computational scheme to study spin excitations in magnetic materials from first principles. The central quantity is the transverse spin susceptibility, from which the complete excitation spectrum, including single-particle spin-flip Stoner excitations and collective spin-wave modes, can be obtained. The susceptibility is derived from many-body perturbation theory and includes dynamic correlation through a summation over ladder diagrams that describe the coupling of electrons and...
Source: http://arxiv.org/abs/1002.4897v1
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Jul 20, 2013
07/13
by
Hongbin Zhang; Frank Freimuth; Gustav Bihlmayer; Stefan Blügel; Yuriy Mokrousov
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Using first principles methods, we investigate topological phase transitions as a function of exchange field in a Bi(111) bilayer. Evaluation of the spin Chern number for different magnitudes of the exchange field reveals that when the time reversal symmetry is broken by a small exchange field, the system enters the time-reversal broken topological insulator phase, introduced by Yang {\it et al.} in Phys. Rev. Lett. 107, 066602 (2011). After a metallic phase in the intermediate region, the...
Source: http://arxiv.org/abs/1203.5025v2
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Sep 18, 2013
09/13
by
Hongbin Zhang; Frank Freimuth; Stefan Blügel; Ivo Souza; Yuriy Mokrousov
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We carry out first-principles calculations which demonstrate the importance of the non-spin-conserving part of the spin-orbit interaction for the intrinsic anomalous Hall conductivity of ordered FePt alloys. The impact of this interaction is strongly reduced if Pt is replaced by the lighter isoelectronic element Pd. An analysis of the interband transitions responsible for the anomalous velocity reveals that spin-flip transitions occur not only at avoided band crossings near the Fermi level, but...
Source: http://arxiv.org/abs/1102.3376v1
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Sep 19, 2013
09/13
by
Hongbin Zhang; Frank Freimuth; Stefan Blugel; Ivo Souza; Yuriy Mokrousov
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We carry out first-principles calculations which demonstrate the importance of spin-flip transitions for the intrinsic anomalous Hall conductivity of ordered FePt alloys. We show the such transitions get enhanced by large spin-orbit coupling of Pt atoms, becoming negligible when Pt is replaced by lighter isoelectronic Pd. We find that spin-flip transitions in FePt originate not only from conventional band anticrossings at the Fermi level, but also from transitions between well-separated pairs...
Source: http://arxiv.org/abs/1009.3184v1
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4.0
Jun 30, 2018
06/18
by
Jan-Philipp Hanke; Frank Freimuth; Chengwang Niu; Stefan Blügel; Yuriy Mokrousov
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Reliable and energy efficient magnetization switching by electrically-induced spin-orbit torques is of crucial technological relevance for spintronic devices implementing memory and logic functionality. Here we predict that the strength of spin-orbit torques and the related Dzyaloshinskii-Moriya interaction in topologically non-trivial magnetic insulators can exceed by far that of conventional metallic magnets. In analogy to the quantum anomalous Hall effect, we explain this extraordinary...
Topics: Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1701.08050
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Sep 21, 2013
09/13
by
Hongbin Zhang; Frank Freimuth; Gustav Bihlmayer; Marjana Ležaić; Stefan Blügel; Yuriy Mokrousov
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Combining tight-binding models and first principles calculations, we investigate the quantum anomalous Hall (QAH) effect induced by intrinsic spin-orbit coupling (SOC) in buckled honeycomb lattice with sp orbitals in an external exchange field. Detailed analysis reveals that nontrivial topological properties can arise utilizing not only spin but also orbital degrees of freedom in the strong SOC limit, when the bands acquire non-zero Chern numbers upon undergoing the so-called orbital...
Source: http://arxiv.org/abs/1301.4426v1
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Jun 29, 2018
06/18
by
Jan-Philipp Hanke; Frank Freimuth; Ashis Kumar Nandy; Hongbin Zhang; Stefan Blügel; Yuriy Mokrousov
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We address the importance of the modern theory of orbital magnetization for spintronics. Based on an all-electron first-principles approach, we demonstrate that the predictive power of the routinely employed "atom-centered" approximation is limited to materials like elemental bulk ferromagnets, while the application of the modern theory of orbital magnetization is crucial in chemically or structurally inhomogeneous systems such as magnetic thin films, and materials exhibiting...
Topics: Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1603.07683
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Jun 29, 2018
06/18
by
Guillaume Géranton; Bernd Zimmermann; Nguyen Hoang Long; Phivos Mavropoulos; Stefan Blügel; Frank Freimuth; Yuriy Mokrousov
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Using the Boltzmann formalism based on the first principles electronic structure and scattering rates, we investigate the current-induced spin accumulation and spin-orbit torques in FePt/Pt and Co/Cu bilayers in the presence of substitutional impurities. In FePt/Pt bilayers we consider the effect of intermixing of Fe and Pt atoms in the FePt layer, and find a crucial dependence of spin accumulation and spin-orbit torques on the details of the distribution of these defects. In Co/Cu bilayers we...
Topics: Mesoscale and Nanoscale Physics, Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1602.03417
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Jun 29, 2018
06/18
by
J. Železný; H. Gao; Aurélien Manchon; Frank Freimuth; Yuriy Mokrousov; J. Zemen; J. Mašek; Jairo Sinova; T. Jungwirth
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One of the main obstacles that prevents practical applications of antiferromagnets is the difficulty of manipulating the magnetic order parameter. Recently, following the theoretical prediction [J. \v{Z}elezn\'y et al., PRL 113, 157201 (2014)], the electrical switching of magnetic moments in an antiferromagnet has been demonstrated [P. Wadley et al., Science 351, 587 (2016)]. The switching is due to the so-called spin-orbit torque, which has been extensively studied in ferromagnets. In this...
Topics: Mesoscale and Nanoscale Physics, Materials Science, Condensed Matter
Source: http://arxiv.org/abs/1604.07590
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Jun 29, 2018
06/18
by
Dongwook Go; Jan-Philipp Hanke; Patrick M. Buhl; Frank Freimuth; Gustav Bihlmayer; Hyun-Woo Lee; Yuriy Mokrousov; Stefan Blügel
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When the inversion symmetry is broken at a surface, spin-orbit interaction gives rise to spin-dependent energy shifts - a phenomenon which is known as the spin Rashba effect. Recently, it has been recognized that an orbital counterpart of the spin Rashba effect - the orbital Rashba effect - can be realized at surfaces even without spin- orbit coupling. Here, we propose a mechanism for the orbital Rashba effect based on sp orbital hybridization, which ultimately leads to the electric...
Topics: Mesoscale and Nanoscale Physics, Condensed Matter
Source: http://arxiv.org/abs/1611.04674
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Jun 28, 2018
06/18
by
Wei Zhang; Matthias B. Jungfleisch; Frank Freimuth; Wanjun Jiang; Joseph Sklenar; John E. Pearson; John B. Ketterson; Yuriy Mokrousov; Axel Hoffmann
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We investigate spin-orbit torques of metallic CuAu-I-type antiferromagnets using spin-torque ferromagnetic resonance tuned by a dc-bias current. The observed spin torques predominantly arise from diffusive transport of spin current generated by the spin Hall effect. We find a growth-orientation dependence of the spin torques by studying epitaxial samples, which may be correlated to the anisotropy of the spin Hall effect. The observed anisotropy is consistent with first-principles calculations...
Topics: Condensed Matter, Materials Science
Source: http://arxiv.org/abs/1508.07906
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Jun 27, 2018
06/18
by
Peter Wadley; Bryn Howells; Jakub Zelezny; Carl Andrews; Victoria Hills; Richard P. Campion; Vit Novak; Frank Freimuth; Yuriy Mokrousov; Andrew W. Rushforth; Kevin W. Edmonds; Bryan L. Gallagher; Tomas Jungwirth
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Louis Neel pointed out in his Nobel lecture that while abundant and interesting from a theoretical viewpoint, antiferromagnets did not seem to have any applications. Indeed, the alternating directions of magnetic moments on individual atoms and the resulting zero net magnetization make antiferromagnets hard to control by tools common in ferromagnets. Remarkably, Neel in his lecture provides the key which, as we show here, allows us to control antiferromagnets by electrical means analogous to...
Topics: Condensed Matter, Mesoscale and Nanoscale Physics, Materials Science
Source: http://arxiv.org/abs/1503.03765
