Fe_{68}Zr_{20}B_{12} amorphous alloy prepared by mechanical alloying technique of 60 h of duration was annealed at different temperatures (420-720°C) during 1 h. Microstructure and magnetic property of as-milled and annealed alloy were investigated by X-ray diffraction, transmission electron microscopy, the Mössbauer spectroscopy and vibrating sample magnetometer techniques. Fe_{68}Zr_{20}B_{12} powders milled during 60 h exhibit amorphous character. After annealing at 420°C, α-Fe phase precipitates from amorphous matrix. Transmission electron microscopy analysis shows the nucleation and growth of α-Fe grains. The Mössbauer results of the annealed alloy at 670°C show that the Fe_3B phase precipitates already and there is still remaining amorphous phase. Coercivity increases with increasing annealing temperature, which is closely related to the microstructures after annealing.
Poly(3-hydroxybutyrate) (PHB) is a semicrystalline biodegradable polymer with chains consisting of methyl (CH₃), methylene (CH₂), methine (CH) and carbonyl (CO) groups. The ¹H-¹³C cross polarization NMR measurements were performed on an as-supplied powder PHB sample at a magic-angle spinning rate of 10 kHz. The measured cross polarization build-up curves and their analysis provided information on the dynamics of ¹H-¹³C NMR cross polarization in functional groups with directly bonded hydrogens. The measurements required setting up the Hartmann-Hahn condition, which was inferred from the Hartmann-Hahn matching profiles measured for each functional group. The cross polarization build-up curves displayed an oscillatory course, which indicates the presence of rigid ¹H-¹³C spin pairs isolated from the lattice. The frequency of the observed oscillations is directly proportional to the ¹H-¹³C dipolar coupling constant, which is related to the C-H distance and its value also reflects the mobility of particular functional groups. The values of dipolar coupling constants were derived from splittings in the Fourier transforms of cross polarization build-up curves. The mobility of particular groups was assessed with the order parameter ⟨S⟩ calculated using experimental and rigid lattice values of dipolar coupling constants.
We employ ^{67}Zn NMR to study distribution of Zn^{2+} in cationic sites of magnetoelectric Y-type hexaferrite single crystal, Ba_{0.5} Sr_{1.5} Zn_2 Fe_{12} O_{22}. The experimental data are interpreted by comparison with NMR spectra simulated from ab initio calculated hyperfine parameters.
The magnetic nanoparticles with core diameter 10 nm were modified by poly-L-lysine to bind antibody for cancer cell detection. Prepared biocompatible magnetic fluid (MFPLL) was characterized by dynamic light scattering method to obtain the particle size distribution. The microstructure of the MNPs and MFPLL samples were studied by transmission electron microscopy, X-ray diffraction and Mössbauer spectroscopy. Magnetic properties of the samples were measured by SQUID magnetometer and superparamagnetic behaviour of the samples was confirmed.
Most of the Fe-nitride phases have been studied in much detail. Nevertheless, there is still a debate about the most efficient, exact and controlled way of obtaining thin films of the desired iron nitride phases. Thin films of iron nitrides were deposited by Molecular Beam Epitaxy in Ultra High Vacuum. By changing the growth parameters we tried to obtain the α"-phase in its purest form. We worked also on iron mononitride, FeN (γ"-FeN) which is known to exist in different phases. The stoichiometry of the samples was determined by means of resonant Rutherford Backscattering Spectroscopy. The samples were studied by room temperature Conversion Electron Mössbauer Spectroscopy. We achieved as much as 24% of pure α"-phase and provide evidence of the existence of γ"-FeN with vacancies and of the transformation of nonmagnetic γ"-phase into magnetic ε-phase after time exposure.
The continued growth of storage capacity requires new innovations in recording media and in particular, in magnetic nanostructures. FePt thin films in the L1_0-phase are interesting candidates for high-density magnetic recording media due to their large magnetocrystalline anisotropy. In the present work, we investigated the magnetic and structural properties of FePt thin films directly grown on MgO(110) with molecular beam epitaxy. The purpose was to gain insight in the correlation between the magnetization process and the morphology of the FePt thin films. We introduce conversion electron MÖssbauer spectroscopy to derive the direction of the easy magnetization axis with respect to the substrate. The results are compared to the characterization performed with high angle X-ray diffraction.
The electron structure and site preferences of Zn and Fe cations in Y hexaferrite system were calculated. The hyperfine magnetic fields on ^{57}Fe nuclei were determined using WIEN2k and corrections for hyperfine contact interaction. The calculated fields were compared to ^{57}Fe nuclear magnetic resonance (NMR) experiment in Ba_2Zn_2Fe_{12}O_{22} single crystal with an aim of interpretation of experimental NMR spectrum.
In this paper the nanocomposites based on Fe-TiC and Fe-TiN which were produced by mechanosynthesis of the mixture of Fe or Fe-N (82 at.%) and Ti (18 at.%) in toluene for 16 h and subsequent compaction have been studied. The structural-phase composition and morphology of the mechanosynthesized powders were studied by X-ray diffraction analysis, the Mössbauer spectroscopy and electron microscopy. It has been shown that powders of the following composition: a solid solution based on Fe, TiC or TiN, a phase on the basis of Fe_{3}C - are formed by mechanosynthesis. The measurements of microhardness and corrosion resistance of the produced compacts were carried out as well.
The paper discusses a theoretical model that associates the shape of the Mössbauer spectrum with the configuration of atoms in local surroundings of the Mössbauer nuclide. Using the model we analyse the Mössbauer spectra of Fe_{72}Al_{28} alloys after various heat treatments. Basing on the model calculations the hyperfine structure parameters describing an effect of an Al atom in the first and the second coordination shell of ^{57}Fe atom are evaluated. Using these parameters the values of hyperfine magnetic field and isomers shift for the atomic configurations present in stoichiometric Fe_3Al are estimated and compared with the results of ab initio calculations.
Iron, an important microelement essential to the functioning of the body, plays a special role in the process of respiration. There are more and more new products available on the pharmaceutical market. Some of them were the subject of previous studies, especially by using the Mössbauer spectroscopy. One of the latest is Biofer. For the present tests three tablets from three different production series of Biofer were used for examination of elemental composition using the X-ray fluorescence and energy dispersive X-ray spectroscopy methods. Information about oxidation of iron contained in the tablets was obtained with by means of the Mössbauer spectroscopy.
In this paper the structural and Mössbauer spectral properties of multiferroic ceramic Bi_5Ti_3FeO_{15} powders prepared by high-energy ball milling of polycrystalline precursor material (mixture of Bi_2O_3, TiO_2 and Fe_2O_3 powders) are presented. Mechanical synthesis was performed by high-energy vibratory mill. The X-ray diffraction methods were applied for the structure characterization of the studied samples. The parameters of diffraction line profiles were determined by PRO-FIT Toraya procedure. The crystallite sizes and lattice distortions were analyzed using the Williamson-Hall method. Investigations of hyperfine interactions in the studied materials were carried out by the Mössbauer spectroscopy. The powder morphology was analyzed by scanning electron microscopy and transmission electron microscopy techniques. It was found that during high-energy milling phase transitions, a decrease in crystallite size and amorphization process are observed.
Magnetoelectric multiferroics are materials which exhibit both magnetic order and ferroelectricity in the same phase. Multiferroic materials, where ferroelectricity and magnetism coexist, were extensively studied. This class of materials offers a large application potential for new devices due to the two coupled degrees of freedom based on the local off-centered distortion and the electron spin. The studied Bi_5Ti_3FeO_{15} ceramics was prepared by conventional synthesis and hot uniaxial pressing reaction applying the conventional mixture of TiO_2, Fe_2O_3 and Bi_2O_3 oxides as precursor materials. The present work focuses on the structure analysis of multiferroic Bi_5Ti_3FeO_{15} ceramics performed by X-ray diffraction method, scanning electron microscopy and the Mössbauer spectroscopy methods.
Fe-based nanoparticles were prepared by laser-driven pyrolysis. The as-synthesised powder consists ofα-Fe and Fe_3O_4/γ-Fe_2O_3 nanoparticles embedded in a pyrolytic carbon matrix. The crystallite size of 1.8 nm forα-Fe was calculated using the Scherrer formula. The as-synthesised nanopowder was superparamagnetic. The maximum of the zero-field cooling curve was observed at 32 K and the distribution of blocking temperatures g(T_B) peaked at 11 K. As a result of small particle sizes and the soft matrix, the Lamb-Mössbauer factor f was significantly higher at 4 K than at 293 K.
Multicomponent single phase alloys were synthesized according to the idea of iron-average atom system. X-ray diffraction shows formation of bcc phase and traces of unidentified phase. Mössbauer spectra indicate presence of two components with different hyperfine magnetic field distributions. The high field component corresponds to the majority ferromagnetic phase. Few per cent of iron builds low field component. The dominant effect of annealing consists in an increase of the low field component.
The multiferroic GaFeO_3 synthesized by a sol-gel method and conventional solid state reaction show remarkably different magnetic transition temperatures. Both samples have orthorhombic crystal structure Pc2_1n. Results of a new analysis of neutron diffraction and Mössbauer data are presented. Full agreement between parameters was achieved using the Mössbauer data as the constraints in the refinement of neutron diffraction data at low and at high temperature. Magnetic moments are reported.
Functionalized multiwall carbon nanotubes as well as nanocomposite based on that material covered by nanoparticles composed of iron oxides were the subject of investigations. In order to identify all iron-bearing phases including those reported on the base of previous X-ray diffraction measurements, the transmission Mössbauer spectroscopy was utilized. The experiments were carried out both at room temperature and also at low temperatures. It was stated that in the investigated nanotubes some impurities were present, originating from the catalyst remains, in form of Fe-C and α -Fe nanoparticles. The Mössbauer spectra collected for the nanocomposite showed a complex shape characteristic of temperature relaxations. The following subspectra related to iron-based phases were identified: sextet attributed to hematite, with hyperfine magnetic field reduced due to the temperature relaxations, sextet corresponding to iron carbide as well as two doublets linked to superparamagnetic hematite and ferrihydrites.
The multi component Fe_{74}Hf_{4}Ta_{1}Cu_{1}Gd_{1}La_{x}Si_{15-x}B_{4} (x = 0, 7) alloys are promising candidates in the search for materials with unusual mechanical and magnetic properties. Amorphous nature of melt-spun samples was confirmed by X-ray diffractometry and Mössbauer spectroscopy. The X-ray diffraction patterns revealed a distinct amorphous halo. The low-field components of magnetic hyperfine field distributions on iron nuclei are observed in the Mössbauer spectra, with average hyperfine field values of 19.9 and 15.7 T for x = 0 and x = 7, respectively. Coercivity studied by vibrating sample magnetometer was about 12 A/m for x = 0 and 82 A/m for x = 7 at 300 K and about 600 A/m for x = 0 and 1200 A/m for x = 7 at 400 K. Remanence also changed with temperature, amounting to 0.64 T for x = 0 and 0.36 T for x = 7 at 300 K, while at 400 K it was 0.43 and 0.11 T for x = 0 and x = 7, respectively. It is shown that La addition has beneficial effect of shifting the Curie point towards lower temperatures together with the increase of magnitude of magnetization.
This paper features investigations into the influence of small additions of alloying elements on: structure, as well as the temporal and thermal stability of magnetic properties, and the disaccommodation effect, for the following amorphous alloys: Fe₆₁Co₁₀Y₈Me₁B₂₀ (where Me = Nb, W). The structure of the investigated samples has been confirmed by the Mössbauer spectroscopy. The obtained results indicate a strong correlation between the structure and the disaccommodation of the studied alloys. The Mössbauer studies reveal different configurations of atoms in the amorphous alloy samples, and the results indicate various potential barriers between orientations of atom pairs. For this reason, to describe the disaccommodation effect, the distribution of activation energy should be taken into account. The distribution of activation energy has been related to the distribution of relaxation times.
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