The magnetic interlayer coupling in La0.7Sr0.3MnO3/SrRuO3 superlattices was investigated. High quality superlattices with ultrathin La0.7Sr0.3MnO3 and SrRuO3 layers were fabricated by pulsed laser deposition. The superlattices grew coherently with Mn/Ru intermixing restricted to about one interfacial monolayer. Strong antiferromagnetic interlayer coupling depended delicately on magnetocrystalline anisotropy and intermixing at interfaces. Ab initio calculations elucidated that the antiferromagnetic coupling is mediated by the Mn-O-Ru bond. The theoretical calculations allowed for a quantitative correlation between the total magnetic moment of the superlattice and the degree of Mn/Ru intermixing.
Chirality-that is, left or right handedness-is present in many scientific areas, and particularly in condensed matter physics. Inversion symmetry breaking relates chirality with skyrmions, which are protected field configurations with particle-like and topological properties. Here we show that a kagome magnet, with Heisenberg and DzyaloshinskiiMoriya interactions, causes non-trivial topological and chiral magnetic properties. We also find that under special circumstances, skyrmions emerge as excitations, having stability even at room temperature. Chiral magnonic edge states of a kagome magnet offer, in addition, a promising way to create, control and manipulate skyrmions. This has potential for applications in spintronics, that is, for information storage or as logic devices. Collisions between these particle-like excitations are found to be elastic at very low temperature in the skyrmionskyrmion channel, albeit without mass-conservation. Skyrmion-antiskyrmion collisions are found to be more complex, where annihilation and creation of these objects have a distinct non-local nature.
The magnetism of 1-ML-thick films of Fe x Co 1−x on Pt͑111͒ was investigated both experimentally, by x-ray magnetic circular dichroism and magneto-optical Kerr effect measurements, and theoretically, by firstprinciples electronic structure calculations, as a function of the film chemical composition. The calculated Fe and Co spin moments are only weakly dependent on the composition and close to 3 B / atom and 2 B / atom, respectively. This trend is also seen in the experimental data, except for pure Fe, where an effective spin moment of only S eff = ͑1.2Ϯ 0.2͒ B / atom was measured. On the other hand, both the orbital moment and the magnetic anisotropy energy show a strong composition dependence with maxima close to the Fe 0.5 Co 0.5 stoichiometry. The experiment, in agreement with theory, gives a maximum magnetic anisotropy energy of 0.5 meV/atom, which is more than 2 orders of magnitude larger than the value observed in bulk bcc FeCo and close to that observed for the L1 0 phase of FePt. The calculations clearly demonstrate that this composition dependence is the result of a fine tuning in the occupation number of the d x 2 −y 2 and d xy orbitals due to the Fe-Co electronic hybridization.
We investigate the magnetic properties of a range of low-dimensional ferromagnets using a combination of first-principles calculations and atomistic spin dynamics simulations. This approach allows us to evaluate the ground state and finite temperature properties of experimentally well characterized systems such as Co/Cu(111), Co/Cu(001), Fe/Cu(001) and Fe/W(110), for different thicknesses of the magnetic layer. We compare our calculated spin wave spectra with experimental data available in the literature, and find a good quantitative agreement. We also predict magnon spectra for systems for which no experimental data exist at the moment, and estimate the role of temperature effects.
In using the fully relativistic versions of the Embedded Cluster and Screened Korringa-KohnRostoker methods for semi-infinite systems the magnetic properties of single adatoms of Fe and Co on Ir(111) and Pt(111) are studied. It is found that for Pt(111) Fe and Co adatoms are strongly perpendicularly oriented, while on Ir(111) the orientation of the magnetization is only out-of-plane for a Co adatom, for an Fe adatom it is in-plane. For comparison also the so-called band energy parts of the anisotropy energy of a single layer of Fe and Co on these two substrates are shown. The obtained results are compared to recent experimental studies using e.g. the spin-polarized STM technique.PACS numbers: 73.20. At, 72.10.Fk, 75.30.Hx, 73.20.Hb The potential application in non-volatile data storage devices is one of the driving forces behind research into magnetic nanostructures. In state-of-the-art hard disk drives a collection of a few hundred of single-domain particles (grains) are used to hold one bit of information. If materials can be manufactured which exhibit sufficiently large anisotropies and thermal stabilities it may become possible to store one bit in a single grain [1]. Such storage devices will require magnetic structures of precise atomic arrangement, as -if in addition the lateral dimensions of grains are further reduced -the influence of the perimeter atoms becomes increasingly important [2,3] and, as is known, from previous studies the magnetic properties of each atom in a nanostructure are highly influenced by its local environment [1,2,3,4].Using Scanning Tunneling Microscopy structures can be precisely tailored and their magnetic properties determined. In recent Scanning Tunneling Spectroscopy experiments [3,5] it has become possible to measure not only the Lande g-factor of individual atoms but also their magnetic anisotropy. The findings suggest that the anisotropy energy of a single atom may eventually be large enough to use the magnetic state of an atom as a storage unit, pushing the ultimate limit for data storage density even further. Since the magnetic properties of small clusters and single adatoms differ strongly from those of bulk systems and even monolayers -e.g. showing a much enhanced magnetic anisotropy energy -they do not only generate interest for their technological relevance but also from a fundamental point of view.In this paper we present a study of the magnetic moments and the angular dependent band energy part of the magnetic anisotropy energy of single atoms of Fe and Co, which -in order to investigate the influence of different substrates -have been deposited on Pt(111) and Ir(111). The calculations have been performed by means of the Embedded Cluster Method (ECM), a scheme based on the fully relativistic Screened Korringa-Kohn-Rostoker (SKKR) method, in which we can treat impurities embedded into a two-dimensional translationally invariant semi-infinite host. This approach makes use of multiple scattering theory in which the electronic structure of a cluster of embedded atoms...
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