This paper is devoted to investigations of the structural and magnetic properties of the Co₂FeAl Heusler alloy produced by three technologies. The alloys prepared by arc and induction melting have resulted in coarse-grained samples in contrast to the fine-grained ribbon-type sample prepared by planar flow casting. Scanning electron microscopy completed by energy dispersive X-ray spectroscopy, X-ray diffraction, Mössbauer spectroscopy, and magnetic methods sensitive to both bulk and surface were applied. The chemical composition was slightly different from the nominal only for the ribbon sample. From the viewpoint of magnetic properties, the bulk coercivity and remnant magnetization have followed the structure influenced by the technology used. Saturation magnetization was practically the same for samples prepared by arc and induction melting, whereas the magnetization of ribbon is slightly lower due to a higher Al content at the expense of iron and cobalt. The surface magnetic properties were markedly influenced by anisotropy, grain size, and surface roughness of the samples. The surface roughness and brittleness of the ribbon-type sample did not make domain structure observation possible. The other two samples could be well polished and their highly smooth surface has enabled domain structure visualization by both magneto-optical Kerr microscopy and magnetic force microscopy.

CeO₂ samples prepared by three technological procedures from the same cerium source, namely cerium (III) nitrate hexahydrate, are studied from the viewpoint of structure, chemical and phase composition, and micro- and macro-magnetic properties. The scanning and transmission electron microscopies completed by energy-dispersive X-ray (EDX) analysis yield nano-structural natures and homogenous chemical compositions of the ceria samples, confirmed also by X-ray diffraction. The diamagnetic, paramagnetic, and ferromagnetic phases in all samples follow from an analysis of the room- and low-temperature measurements of hysteresis loops. Iron impurities in ppm amounts are clearly detected by ⁵⁷Fe Mössbauer spectrometry not only in the ceria samples but also in the selected input chemicals used for their preparation. This contributes to the explanation of the magnetic behaviour of nanosized ceria.

Quantum-mechanical calculations are applied to examine magnetic and electronic properties of phases appearing in binary Fe-Al-based nanocomposites. The calculations are carried out using the Vienna Ab-initio Simulation Package which implements density functional theory and generalized gradient approximation. The focus is on a disordered solid solution with 18.75 at. % Al in body-centered-cubic ferromagnetic iron, so-called $\alpha$ -phase, and an ordered intermetallic compound Fe ${}_3$ Al with the D0 ${}_3$ structure. In order to reveal the impact of the actual atomic distribution in the disordered Fe-Al $\alpha$ -phase three different special quasi-random structures with or without the 1st and/or 2nd nearest-neighbor Al-Al pairs are used. According to our calculations, energy decreases when eliminating the 1st and 2nd nearest neighbor Al-Al pairs. On the other hand, the local magnetic moments of the Fe atoms decrease with Al concentration in the 1st coordination sphere and increase if the concentration of Al atoms increases in the 2nd one. Furthermore, when simulating Fe-Al/Fe ${}_3$ Al nanocomposites (superlattices), changes of local magnetic moments of the Fe atoms up to 0.5 ${\mathsf{\mu }}_{\mathrm{B}}$ are predicted. These changes very sensitively depend on both the distribution of atoms and the crystallographic orientation of the interfaces.

Microstructural and magnetic properties of the X₂YZ, namely Fe₂MnSi and Fe₂MnAl, Heusler alloys have been studied from the viewpoint of technology for their production and for the Z element effect. First, arc melting was applied to produce button-type ingots from which samples in a form of 500 µm thick discs were cut. Second, planar flow casting technology yielded samples in a ribbon-form 2 mm wide and 20 μm thick. The checked area chemical compositions were in agreement with the nominal ones. Nevertheless, the darker square objects and smaller bright objects observed at the wheel side of the Fe₂MnSi ribbon sample yielded higher Mn content at the expense of Fe. The X-ray diffraction patterns of all samples have indicated L2₁ structure with lattice parameters, 0.567 (1) nm for Fe₂MnSi and 0.584 (1) nm for Fe₂MnAl, being within an experimental error independent of production technology. On the other hand, the technology has markedly influenced the microstructure clearly pointing to the larger size of grains and grain boundaries in the disc samples. From the magnetic viewpoint, both alloys are paramagnetic at room temperature without visible influence of their production. On the contrary, the low-temperature behavior of the microscopic hyperfine parameters and the macroscopic magnetic parameters exhibits differences affected by both chemical composition and microstructure.