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The X/Co 3 nm/Y (where X, Y = Au, Pt) trilayers with as deposited in-plane magnetization alignment were irradiated with 30 keV Ga+ ions in the wide range of ion fluence. The samples were investigated by means of complementary techniques: magneto-optical magnetometry and spectroscopy (in the photon energy range from 1.2 eV to 4.5 eV), magnetic force microscopy, positron annihilation spectroscopy, x-ray diffraction and reflectivity. Difference in miscibility of interface atoms is clearly manifested in various intermixing extent at Co/Pt and Co/Au interfaces and consequently in magnetic properties of the irradiated trilayers. Low irradiation fluence (∼1014 ions cm−2) leads to ∼1 nm interfaces broadening without visible surface etching for all samples, which is related with a distinct drop of magnetic anisotropy. However, the high irradiation fluence (∼5 × 1015 ions cm−2) results in enhanced interface broadening and significant surface etching (∼5 nm) partially removing also Co atoms. Tensile strains (up to 0.5%) were developed in the cover layers. The tensile strain, layers intermixing and the creation of Co–Pt(Au) alloys with different composition formed by irradiation are correlated with the increase of magnetic anisotropy. Moreover it was observed that substitution of Au instead of Pt (as a cap or buffer layer) results in substantial increase of perpendicular magnetic anisotropy. Maximal increase of magnetooptical parameters was observed for Pt/Co/Pt layer. Irradiation induced changes of concentration profiles are revealed using magnetooptical spectra, x-ray reflectivity spectra and simulations with use of binary collision approximation.

To succeed in the next generation of magnetic storages, nanomagnetic structures must be engineered to allow modulation of magnetization amplitude and spatial period. We demonstrate computationally how magnetic nanostructures states (domains with narrow wall, skyrmions, spin spirals, conical spin spirals, and in-plane magnetization configuration) can be designed in ultrathin films with a Dzyaloshinskii–Moriya interaction (DMI) by adjusting two material parameters: perpendicular magnetic anisotropy characterized by the quality factor Q, and reduced DMI constant Δ . For a broad range of Q and Δ parameters, the magnetization states are mapped in (Q, Δ ) diagrams and characterized by the periodicity (p) of spatial distribution of magnetization and the mean value of the square of an out-of-plane normalized magnetization component 〈 m z 2 〉 . We explain the transitions between different magnetization states and describe phase transition curves in terms of vanishing of the domain wall energy for both 0 ≤ Q < 1 and Q > 1 cases. We show that by changing Δ and/or Q and approaching the phase transition curves, the discontinuous transitions accompanied by jumps of both period and amplitude take place.

We describe synthesis of submicron Y3Fe5O12 (YIG) films sputtered on GaAs-based substrates and present results of the investigation of ferromagnetic resonance (FMR), spin wave propagation and interaction between spin excitations and 2D electrons in interface layer in YIG / AlOx / GaAs-heterostructures. It is found that the contribution of the relaxation process to the FMR linewidth is about 2 % of the linewidth \Delta H. At the same time, for all samples FMR linewidths are high. Sputtered YIG films have magnetic inhomogeneity, which gives the main contribution to the FMR linewidth. Transistor structures with two-dimensional electron gas (2DEG) channels in AlOx / GaAs interface governed by YIG-film spin excitations are designed. An effective influence of spin excitations on the current flowing through the GaAs 2DEG channel is observed. Light illumination results in essential changes in the FMR spectrum. It is found that an increase of the 2DEG current leads to an inverse effect, which represents essential changes in the FMR spectrum., Comment: 7 pages, 6 figures

We suggest the creation of a Global Web Laboratory (we call it GloLab) for scientific purposes and teaching experiments online. In this article, we discuss the main principles and problems of building such a global Internet-laboratory. An example of a current working laboratory for teaching magnetism experiments online is also discussed.

We describe our experience in building a remote laboratory for teaching magnetic domains. Fulfilling the proposed on-line experiments, students can observe and study magnetization processes that are often difficult to explain with written material. It is proposed that networks of remotely accessible laboratories could be integrated in the Global Laboratory which could make research and education closer as well as disseminate knowledge and research results to a non-expert audience.

We have investigated theoretically (with micromagnetic simulations and plane wave method) and experimentally (with ferromagnetic resonance and Brillouin light scattering) three types of antidot lattices (ADLs) based on permalloy thin films with increased complexity of the unit cell: simple square, bi-component square and wave-like ADL. We have found that placing a small additional antidot in the center of the unit cell of the square ADL modify significantly the spin wave spectrum and its dependence on the orientation of the in-plane magnetic field. We also check the further changes of spin wave spectrum resulting from the introduction of air-gaps connecting small and large antidots. In particular, the presence of small antidots change the dependence of the frequency of the fundamental mode on the angle of the in-plane applied magnetic field. The air-gaps strongly discriminates the propagation of spin waves in two principal direction of ADL lattice, orthogonal to each other. In spite of these spectral changes, the spatial distribution of the spin wave amplitude generally preserves some similarities for all three structures. We also highlighted out the role of defects in the ADL in the observed spectra. The obtained results can be interesting for the magnonics applications of the magnonic crystals., 22 pages, 10 figures and submitted to Physical Review Letters B

The effects of shape and geometry of antidot (square, bi-component, and wave-like) lattices (ADLs) on the magnetization reversal processes and magnetic anisotropy has been systematically investigated by magneto-optical Kerr effect based microscopy. Our experimental results were reproduced by micromagnetic simulations, which highlight the qualitative agreement with the experimental results. We have demonstrated that a small antidot in the center of a unit cell in the square ADL is sufficient to induce additional easy axes with large coercive fields. In wave-like patterns, narrow channels connecting smaller and larger antidots (bi-component ADL) further drastically change the anisotropy map, creating the high coercive fields along a wide angular range (90°) of directions parallel to the channels. In simulated results, we have observed formation of periodic domain structures in all ADLs, however, in the case of a wave-like pattern it is most regular and moreover two different periodic patterns are stabilized at different applied magnetic field values. The formation of 360° domain walls were also observed in wave-like ADL where these domains are formed along the lines connecting adjacent larger and smaller antidots, perpendicular to the channels. These findings point out the possibility of exploiting ADLs with complex unit cells in magnonic or spintronic applications.

An irreversible rotation of magnetization from in-plane to an out-of-plane direction was induced in Pt/Co/Pt epitaxial trilayers by single and multiple pulses of extreme ultraviolet (EUV) irradiations. The radial dependence of remanence, coercivity and saturation fields across the irradiated spots was studied with the help of magneto-optical techniques for the samples with various Co and Pt buffer layer thicknesses. The sample surface and magnetic ordering were investigated using atomic force and magnetic force microscopies. Based on magnetic and morphological changes, the residual stress after thermoplastic deformation in the spot area is discussed as a reason for the observed transformation.

We describe the synthesis of submicron Y3Fe5O12 (YIG) films sputtered on GaN-based substrates and present the results of the investigation of ferromagnetic resonance (FMR) and spin wave propagation in YIG / GaN structures. It is found that spin waves propagated in deposited YIG films have low damping. At the frequency of 3.2 GHz the spin-wave damping parameter is less than � � 3.4 10 4 . Sputtered YIG films have magnetic inhomogeneity, which gives the main contribution to the FMR linewidth. The FMR linewidth increase caused by the relaxation process is insignificant and is equal to low values (2.2– 3.7% of the linewidth). The low relaxation of spin waves in deposited YIG films gives the opportunity to construct tuneable spin-wave band-pass filters with a high-quality factor on GaN substrates and to design radiation-tolerant monolithic microwave integrated circuits.

The novel method for fabricating magnetic dots reported in this work exploits the dependence of the magnetic anisotropy of an ultrathin Co film on its thickness and on the type of the buffer layer. A patterned buffer prepared as self-assembled Au islands with a lateral size of several hundred nanometres grown on a Mo film surface induces mono-domain dots magnetized perpendicularly to the film plane in the epitaxial Co layer. Polar magneto-optical Kerr magnetometry and magnetic force microscopy have been used to investigate the magnetization reversal of the dots. Nucleation of the reversed magnetic domain followed by the unpinned movement of domain walls is discussed as a possible mechanism responsible for magnetization switching.

In this paper we calculate the pinning field associated with domain wall motion in ultrathin magnetic films, which is controlled by a high density, n, of weak defects. The pinning field is shown to vary as n5/6d−1/2, d being the thickness of the magnetic layer. This model is applied to a Au/Co/Au ultrathin film structure with perpendicular anisotropy, close to the spin reorientation transition.

Unexpectedly small velocities of demagnetisation processes have been observed in Y2Ca1Fe39Co0.1Ge1O12 films. These phenomena have been investigated in the experimental set-up based on the Faraday effect. The investigated after-effects have been numerically analysed in terms of continuous distribution of relaxation times tau . Strong dependences of tau on temperature and applied magnetic field have been found. The activation character of relaxation processes has been determined.

The coexistence of the ferrimagnetic and the antiferromagnetic phases has been observed in the DyFeO3 orthoferrite. The observations were made in a polarization microscope by means of the Faraday effect. Several features of the spin reorientation which shed some light on the mechanism of the transition, have been observed.