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There is a growing interest in mixing spintronics and superconductivity to develop original energy-efficient nonvolatile memory and logic devices. Research works conducted so far have mostly focused on superconductor with critical temperature Tc lower than 10 K. Here, we report on the growth and characterization of MgB2/Ni80Fe20 and MgB2/Co bilayers, where Tc of the MgB2 layer is of the order of 30 K. Ferromagnetic resonance was undertaken to analyze the spin pumping into MgB2. The larger magnetization at saturation in Co, as compared to Ni80Fe20, induces a smaller spin pumping contribution to the damping when MgB2 is normal. A spin pumping reduction was observed for both bilayers when MgB2 becomes superconductor and is attributed to the opening of the superconducting gap. The present results show that MgB2 thin films could be suitable to implement superconducting spintronic at 30 K, which is not only relevant for future technological development but also relaxes experimental constraints related to low-temperature investigations. [ABSTRACT FROM AUTHOR]

Ultrafast studies of magnetization dynamics have revealed fundamental processes that govern spin dynamics, and the emergence of time-resolved x-ray techniques has extended these studies to long-range spin structures that result from interactions with competing symmetries. By combining time-resolved resonant x-ray scattering and ultrafast magneto-optical Kerr studies, we show that the dynamics of the core spins in the helical magnetic structure occur on much longer time scales than the excitation of conduction electrons in the lanthanide metal Dy. The observed spin behavior differs markedly from that observed in the ferromagnetic phase of other lanthanide metals or transition metals and is strongly dependent on temperature and excitation fluence. This unique behavior results from coupling of the real-space helical spin structure to the shape of the conduction electron Fermi surface in momentum space, which creates a bottleneck in spin scattering events that transfer the valence excitation to the core spins. The dependence of the dynamics on the intersite interactions renders the helical ordering much more robust to perturbations than simple ferromagnetic or antiferromagnetic ordering, where dynamics are driven primarily by on-site interactions.

The formation of two-dimensional oxide dodecagonal quasicrystals as well as related complex approximant phases was recently reported in thin films derived from BaTiO3 or SrTiO3 perovskites deposited on (111)-oriented Pt single crystals. Here, we use an all-thin-film approach in which the single crystal is replaced by a 10 nm thick Pt(111) buffer layer grown by molecular beam epitaxy on an Al2O3(0001) substrate. An ultra-thin film of SrTiO3 was subsequently deposited by pulsed laser deposition. The film stacking and structure are fully characterized by diffraction and microscopy techniques. We report the discovery of two new complex phases obtained by reduction of this system through high temperature annealing under ultrahigh vacuum conditions. The formation of a new large square approximant with a lattice parameter equal to 44.4 Å is evidenced by low-energy electron diffraction and scanning tunneling microscopy (STM). Additionally, a new 2D hexagonal approximant phase with a lattice parameter of 28 Å has been observed depending on the preparation conditions. Both phases can be described by two different tilings constructed with the same basic square, triangle and rhombus tiles possessing a common edge length of about 6.7 Å. Using the tiling built from high resolution STM images, we propose an atomic model for each approximant which accounts for the experimental observations. Indeed, the STM images simulated using these models are found to be in excellent agreement with the experimental ones, the bright protrusions being attributed to the topmost Sr atoms. In addition our theoretical approach shows that the adhesion of the oxide layer is rather strong (−0.30 eV Å−2). This is attributed to charge transfer, from the most electropositive elements (Sr and Ti) to the most electronegative ones (Pt and O), and to hybridization with Pt-states. Density of states calculations indicate differences in the electronic structure of the two approximants, suggesting different chemical and physical properties. This all-thin-film approach may be useful to explore the formation of complex two-dimensional oxide phases in other metal-oxide combinations. [ABSTRACT FROM AUTHOR]

(110) europium films exhibit an atypical magnetic arrangement at low temperature, characterized by a low magnetization value from macroscopic magnetization measurements. An accurate analysis of the temperature and magnetic field range, where this specific configuration is stabilized, has shown that it is favored by a small Eu thickness. A two-helices configuration with propagation vectors along [100] and [010] may explain this low magnetization state. Index Terms--Epitaxial layers, magnetic films, magnetoelasticity, thin films.

The long-range magnetic order is found in superlattices of two dissimilar magnetic rare earth metals, Er and Dy. The Dy spin coupling is capable of being propagated through Er when Er is subjected to paramagnetic conditions. Distinct ordering temperatures similar to bulk counterpart elements are exhibited by the Er and Dy layers. Both rare earth elements exhibit identical magnetic periodicity.

Neutron scattering experiments using a two-dimensional detector are used for measuring a nuclear Bragg peak and its six surrounding magnetic satellites in (110)europium film. The thermal history of the film has dramatic consequences on the magnetic configurations, correlated with lattice clamping effects persisting above the magnetic ordering temperature.

High resolution and grazing incidence x-ray scattering experiments are performed to examine the magnetostructural coupling in (110) europium film. The grazing incidence is used for showing that the structural characteristics are nonhomogeneous with the film depth, the dominant structural domain being different in the top and bottom parts of the film.

The magnetic anisotropy can be tailored in magnetic films by the proper choice of the substrate and single crystalline (111)Sm[Al.sub.2] films are grown by molecular beam epitaxy on two substrates. The direction of the anisotropy can be modified by changing the substrate of the given magnetic film.

The magnetic properties of thin film of europium are investigated and the evidence of modifications in the domain population originating directly from deformations induced by epitaxial strain is presented. It is found that the application of magnetic field modifies the population of the domains giving rise to unusual irreversible effects.

The variation of the magnetization vector with depth into DyFe2/YFe2 superlattice, in which the magnetization of the soft YFe2 dominates the magnetic structure, is investigated. The result showed that the magnetization of the YFe2 component is nearly always saturated, flipping directly from positive to negative saturation, while the net magnetization of the hard DyFe2 component significantly varies in high fields and is probably nonuniform.

The thermal evolution of the magnetization reversal process in a superlattice [DyFe2 (50 Angstrom)/Fe2 (200 Angstrom)] is discussed. The magnetization in the hard layers reverses in positive field at high-temperature regime.