Search results for "ddc:5"
showing 10 items of 1717 documents
Magnetism of monomer MnO and heterodimer FePt@MnO nanoparticles
2017
We report about the magnetic properties of antiferromagnetic (AF) MnO nanoparticles (NPs) with different sizes (6--19 nm). Using a combination of polarized neutron scattering and magnetometry, we were able to resolve previously observed peculiarities. Magnetometry, on the one hand, reveals a peak in the zero-field-cooled (ZFC) magnetization curves at low temperatures $(\ensuremath{\sim}25$ K) but $no$ feature around the N\'eel temperature at 118 K. On the other hand, polarized neutron scattering shows the expected behavior of the AF order parameter vanishing around 118 K. Moreover, hysteresis curves measured at various temperatures reveal an exchange-bias effect, indicating a coupling of an…
Orbital Rashba effect in a surface-oxidized Cu film
2020
Recent experimental observation of an unexpectedly large current-induced spin-orbit torque in surface oxidized Cu on top of a ferromagnet pointed to a possibly prominent role of the orbital Rashba effect (ORE) in this system. Here, we use first principles methods to investigate the ORE in a system of oxygen monolayer deposited on top of a Cu(111) film. We show that surface oxidization of the Cu film leads to a gigantic enhancement of the ORE near the Fermi energy. The resulting chiral orbital texture in the momentum space is exceptionally strong, reaching as much as $\ensuremath{\sim}0.5\ensuremath{\hbar}$ in magnitude. We find that resonant hybridization between O $p$ states and Cu $d$ sta…
Spin-orbit torques and tunable Dzyaloshinskii-Moriya interaction in Co/Cu/Co trilayers
2017
We study the spin-orbit torques (SOTs) in Co/Cu/Co magnetic trilayers based on first-principles density-functional theory calculations in the case where the applied electric field lies in-plane, i.e., parallel to the interfaces. We assume that the bottom Co layer has a fixed in-plane magnetization, while the top Co layer can be switched. We find that the SOT on the top ferromagnet can be controlled by the bottom ferromagnet because of the nonlocal character of the SOT in this system. As a consequence the SOT is anisotropic, i.e., its magnitude varies with the direction of the applied electric field. We show that the Dzyaloshinskii-Moriya interaction (DMI) in the top layer is anisotropic as …
Mechanism for ultrafast electric-field driven skyrmion nucleation
2021
We show how a Dzyaloshinskii-Moriya interaction can be generated in an ultrathin metal film from a femtosecond pulse in electric field. This interaction does not require structural inversion-symmetry breaking, and its amplitude can be tuned depending on the amplitude of the field. We perform first-principles calculations to estimate the strength of the field-induced magnetoelectric coupling for ferromagnetic Fe, Co, and Ni, and antiferromagnetic Mn, as well as FePt and MnPt alloys. Last, using atomistic simulations, we demonstrate how an isolated antiferromagnetic skyrmion can be coherently nucleated from the collinear background by an ultrashort pulse in electric field on a hundred-femtose…
Colloids as model systems for liquid undercooled metals
2009
Physical review / E 79(1), 4 (2009). doi:10.1103/PhysRevE.79.010501
Bulk spin polarization of magnetite from spin-resolved hard x-ray photoelectron spectroscopy
2021
Physical review / B 104(4), 045129 (1-10) (2021). doi:10.1103/PhysRevB.104.045129
Ferromagnetic and paramagnetic magnetization of implanted GaN:Ho,Tb,Sm,Tm films
2015
The SQUID magnetic measurements were performed on the GaN films prepared by metal-organic vapour phase epitaxy and implanted by Tb3+, Tm3+, Sm3+, and Ho3+ ions. The sapphire substrate was checked by the electron paramagnetic resonance method which showed a content of Cr3+ and Fe3+ impurities. The samples 5 × 5 mm2 were positioned in the classical straws and within an estimated accuracy of 10−6 emu, no ferromagnetic moment was detected in the temperature region of 2–300 K. The paramagnetic magnetization was studied for parallel and perpendicular orientation. In the case of GaN:Tb sample, at T = 2 K, a pronounced anisotropy with the easy axis perpendicular to the film was observed which can b…
Synergistic Effects of Surface Coating and Bulk Doping in Ni-Rich Lithium Nickel Cobalt Manganese Oxide Cathode Materials for High-Energy Lithium Ion…
2022
Ni-rich layered oxide cathodes are promising candidates to satisfy the increasing energy demand of lithium-ion batteries for automotive applications. Thermal and cycling stability issues originating from increasing Ni contents are addressed by mitigation strategies such as elemental bulk substitution ("doping") and surface coating. Although both approaches separately benefit the cycling stability, there are only few reports investigating the combination of two of such approaches. Herein, the combination of Zr as common dopant in commercial materials with effective Li2 WO4 and WO3 coatings was investigated with special focus on the impact of different material processing conditions on struct…
Charge Transport Layers Limiting the Efficiency of Perovskite Solar Cells: How To Optimize Conductivity, Doping, and Thickness
2019
Perovskite solar cells (PSCs) are one of the main research topics of the photovoltaic community; with efficiencies now reaching up to 24%, PSCs are on the way to catching up with classical inorganic solar cells. However, PSCs have not yet reached their full potential. In fact, their efficiency is still limited by nonradiative recombination, mainly via trap-states and by losses due to the poor transport properties of the commonly used transport layers (TLs). Indeed, state-of-the-art TLs (especially if organic) suffer from rather low mobilities, typically within 10(-5) and 10(-2) cm(-2) V-1 s(-1), when compared to the high mobilities, 1-10 cm(-2) V-1 s(-1), measured for perovskites. This work…
Local structure of copper nitride revealed by EXAFS spectroscopy and a reverse Monte Carlo/evolutionary algorithm approach
2016
Physica scripta 91(5), 054003 (2016). doi:10.1088/0031-8949/91/5/054003