Our study presents experimental results on Co2MnSi thin-film preparation and resulting magnetic properties of the Co2MnSi Heusler alloy. The focus of our work is on the important role of the microstructure and the magnetic properties relationships of Co2MnSi thin films prepared using dc magnetron sputtering. We examined the microstructure evolution determined with x-ray diffraction for various substrates, e.g., MgO, SrTiO3, Si and SiO2, at different substrate temperatures. Polycrystalline growth observed at high substrate temperatures is independent of the nature and orientation of the substrate. These films show soft magnetic behavior at a net magnetization of 4.12μB. In contrast, textured growth is obtained at room temperature by introducing a vanadium seed layer. These samples are magnetically harder but possess a magnetization of 0.25μB only. This behavior indicates a two phase film consisting of an amorphous and textured volume. Consequently, sputtering at low argon pressure at high temperature result in very smooth Co2MnSi Heusler films, enabling the Co2MnSi Heusler alloys to serve as electrodes in tunnel magnetoresistance structures.

The magnetic and structural properties of Fe/Si multilayers (Mls) have been studied by x-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS) methods. Strong antiferromagnetic (AF) coupling J=−1.93 mJ/m2 accompanied by saturation field of 1.5 T has been found for Si layer thickness dSi=1.4 nm. Magnetic moment measurements of Fe/Si Mls vs Fe thickness revealed that 0.25 nm of Fe per single interface is magnetically inactive. The CEMS spectra recorded at room temperature consist of the Zeeman sextet characteristic of the pure Fe phase (hyperfine field of about 32.8 T) accompanied by two spectral components related to FeSi system: magnetic broad sextet and a quadrupole doublet. The broad sextet could originate from various Fe sites at the interface. The nonmagnetic quadrupole split (QS) doublet is most probably associated with the nonstoichiometric c-Fe1−xSix phase. For larger Si layer thickness (dSi>2 nm) the spectral contribution of the QS doublet increases from 5.7% to about 16%.

Co nanocrystals have been prepared via two different chemical preparation routes. Microstructural characterization has been carried out by conventional and high-resolution transmission electron microscopy. Magnetic characterization reveals that Co nanocrystals with mean particle size distributions about 6 nm are ferromagnetic at room temperature. Superlattices of about 1 m 1 m can be reproduced. For the second preparation route the formation of an -Co phase was detected by X-ray diffraction. Whereas the pure Co nanocrystals form domains with a mixture of simple cubic and hexagonal packing, FeCo alloyed nanoparticles form long chain-like structures.

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Offering the possibility of improving data storage and magnetic sensoric, applications of giant magnetoresistance (GMR) in thin metallic films are of great interest. In order to study thermal reactions in such layered structures, atom probe tomography is used, which has been proven to perform a real three-dimensional analysis on the relevant length scale of several angstroms only. Co/Cu/Ni79Fe21 layered structures were deposited on tungsten substrate tips by ion beam sputtering and analyzed in the as-prepared state and after suitable heat treatments. After annealing at 250 °C for 30 min, Fe segregation at the Co/Cu interface inside the Co layer is clearly observed. This effect may be interpreted as an interface dusting potentially increasing the GMR. After annealing at 350 °C for 30 min, an additional Ni segregation inside Cu grain boundaries is observed. It is suggested that this segregation path forms the initial stage of pinhole formation and finally causes ferromagnetic bridges through the paramagnetic coupling layer.