The structure, hyperfine interactions and magnetic properties of the series of multiferroic Bim+1Ti3Fem−3O3m+3 Aurivillius compounds with m=4–8 were studied using X-ray diffraction, 57Fe Mössbauer ...spectroscopy and vibrating sample magnetometry. Samples were prepared by the conventional solid-state sintering method. Bulk magnetic measurements showed that for m=4 the compound is paramagnetic down to 2K while in the compound with m=5 the antiferromagnetic type transition was observed at 11K. In the case of compounds with m=6–8 much more complex magnetic behavior was found. For these compounds a gradual spin freezing and antiferromagnetic spin glass-like ordering were observed on decreasing temperature. The temperature of spin glass freezing was determined as 260, 280 and 350K for m=6, 7 and 8, respectively. Room-temperature Mössbauer spectra of all the compounds studied confirm their paramagnetic state. However, liquid nitrogen and liquid helium temperature measurements reveal magnetic ordering with a residual paramagnetic phase contribution for the compounds with m=5–8.
•Aurivillius compounds prepared by solid-state sintering.•Coexistence of antiferromagnetic and paramagnetic phases seen by Mössbauer spectra.•Hyperfine interactions parameters of compounds determined.•Antiferromagnetic spin glass-like ordering observed down to 10K.
Tribological properties of titanium and alloy Ti6Al4V are changed by the irradiation with 160 MeV swift xenon ions. At the beginning of the tribological test, the friction coefficient of titanium is ...reduced. As the test of titanium proceeds, an unconventional two-step increase in its value is observed. The irradiation causes oscillating changes in the crystal lattice parameters of titanium and Ti6Al4V. These unconventional changes result from the annealing and evolution of radiation defects during irradiation with a high fluence of Xe ions. The two-step changes in the friction coefficient of titanium and the unconventional changes in the crystal lattice parameters of Ti and Ti6Al4V following the swift Xe-ion irradiation have been observed for the first time.
•Two-step changes in the friction coefficient of Ti irradiated with swift Xe ions.•Lattice parameters of Ti6Al4V undergo oscillating changes with increasing ion dose.•This effect is the result of annealing and evolution of radiation defects.
The microstructure and corrosion properties of Fe-Cr-Si alloys prepared by mechanical alloying method were studied using the 57Fe transmission Mössbauer spectroscopy (TMS), x-ray diffraction (XRD), ...and scanning electron microscope (SEM). The initial ternary mixture in Fe:Cr:Si atomic ratio of 85:10:5 was prepared on the basis of high-purity Fe, Cr, and Si powders. The studied samples were obtained after 10 h (MA-10h), 20 h (MA-20h), and 50 h (MA-50h) of alloying process in planetary ball mill. The SEM results indicate that the mean particle size of prepared material is strongly dependent on milling time and the estimated mean particle sizes were 15.4 (±3.0) μm, 9.0 (±1.5) μm, and 1.73 (±23) μm for MA-10h, MA-20h, and MA-50h, respectively. The XRD and TMS measurements reveal that all the prepared powders are alloys with body-centered cubic (bcc) structure. Moreover, TMS was used to investigate corrosion of Fe-Cr-Si powders during exposure to air at high temperature. The obtained results suggest that reduction of mean particle size of mechanically synthesized alloy drastically decreases its corrosion resistance properties. Finally, the hyperfine field distributions p(B) obtained for MA-10h, MA-20h, and MA-50h samples before and after annealing were compared with the simulated p(B) for a random bcc Fe0.85Cr0.10Si0.05 alloy. This comparison shows that the amount of Cr and Si atoms dissolved in Fe-Cr-Si bcc alloy changes significantly with time of mechanical alloying as well as with annealing.
The magnetic properties of magnetite nanoparticles (Fe
3
O
4
NPs) strongly depend on their chemical and physical parameters, which can be regulated by a controlled synthesis process. To improve the ...quality of the obtained nanoparticles, their surface is often modified with organic compounds (from the group of surfactants, sugars, proteins, or organic acid). In this study, we synthesized magnetite nanoparticles with a surface modified with the organic compound DMSA. Then, the nanocrystallites were characterized in terms of structure and morphology. To investigate the role of DMSA and to understand the adsorption mechanism, FTIR measurements were carried out. Using Mössbauer spectroscopy, we investigated temperature-induced changes in the magnetic properties of prepared samples. The spectra were recorded in a wide temperature range (from 4 K to 390 K) for two types of samples: powders and ferrofluids with various concentrations. In the case of powder samples, the superparamagnetic doublet appeared at room temperature. For magnetic suspensions, the spectra were more complicated. They consisted of superposition of asymmetrically broadened sextets and doublets, which was caused by the occurrence of long-range dipole-dipole interactions. These interactions affected the magnetic properties of the material and increased the blocking temperature. Additionally, the magnetic hysteresis and zero field cooling-field cooling (ZFC/FC) curves were measured with the use of a vibrating sample magnetometer.
The magnetic and magnetocaloric characteristics of the Mn
1.9
Cu
0.1
Sb alloy were studied. The presence of a relatively sharp decrease in the magnetization in the region of 100 K is established, ...which, according to ab initio calculations, can be interpreted as antiferromagnetism–ferrimagnetism transitions. The presence of a magnetic phase transition from a ferrimagnetic to an antiferromagnetic state (F ↔ AF) leads to the appearance of an inverse magnetocaloric effect, which is preserved in magnetic fields up to 10 T.
The analysis of 57Fe Mössbauer spectroscopy results for cation and anion substituted Mn2-xFexP1-yAsy was done in order to find out the influence of the Mn/Fe ratio on the magnetic properties of solid ...solutions and to compare experimental hyperfine parameters with those calculated from firstprinciples.The correlation between third Mössbauer sextet in Mn2-xFexP0.5As0.5 spectrum at 77K and stabilization of the antiferromagnetic phase for x = 0.5-0.6 was found on the basis of comparison between the magnetic phase diagrams and the "hyperfine field - iron content" dependence. The observed qualitative difference for Mn2-xFexP0.5As0.5 and MnFeAsyP1-y "hyperfine field - concentration" diagrams was interpreted on the basis of different mechanisms of magnetic phase stabilization and the different configurations of tetrahedral anionic environment of iron ions for systems with cation and anion substitutions.
Three different methods were used to obtain Bi
Ti
FeO
ceramics, i.e. solid-state sintering, mechanical activation (MA) with subsequent thermal treatment, and electrical discharge assisted mechanical ...milling (EDAMM). The structure and magnetic properties of produced Bi
Ti
FeO
samples were characterized using X-ray diffraction and Mössbauer spectroscopy. The purest Bi
Ti
FeO
ceramics was obtained by standard solid-state sintering method. Mechanical milling methods are attractive because the Bi
Ti
FeO
compound may be formed at lower temperature or without subsequent thermal treatment. In the case of EDAMM process also the time of processing is significantly shorter in comparison with solid-state sintering method. As revealed by Mössbauer spectroscopy, at room temperature the Bi
Ti
FeO
ceramics produced by various methods is in paramagnetic state.
(Ti,Al)N layers thinner than 0.35
μm were deposited on the Ti or Al substrates with the aluminium or titanium ion beam-assisted deposition (IBAD) method. Directly after the implantation, phase mixing ...was observed on the top sample layer. Mainly a layer of c-Ti
1−
x
Al
x
N was formed on the surface of both samples. Underneath, there was a c-TiN layer on the titanium substrate and a c-AlN layer on the aluminium substrate. After annealing at 450
°C for 48
h, the internal layer in the sample deposited on the Ti substrate decomposed, forming a structure containing a mixture of the c-TiN and c-AlN phases. Annealing the sample made on the Al substrate caused a transformation of the external layer into Ti
2AlN. Aluminium deposition on the aluminium substrate and nitrogen implantation led to the formation of the c-AlN phase. The process of sample annealing caused a partial transformation of the cubic phase (c-AlN) into a thermodynamically stable hexagonal h-AlN phase. The top layer of all tested samples had a columnar structure. Annealing led to a change in the column density and height.
(MnZn)1 a x Fe x Sb solid solutions with the Cu2Sb structure have been prepared through heterophase reactions. Their stability range is 0 < x less than or equal to 0.2. The magnetic interaction in ...the solid solutions has a ferromagnetic character. The Curie temperature and mass magnetization of the solid solutions have been determined, and the iron dopant has been shown not to participate in magnetic interaction.
(Ti,Cr)N and (Al,Cr)N thin films were prepared by nitrogen ion beam assisted deposition of Cr, Ti or Al (IBAD) atoms on a titanium, chromium or aluminium substrate. In this way, layers featuring a ...diverse composition were obtained. The actual profile of the implanted and deposit atoms differed from the theoretically assumed process. Some of the implanted nitrogen formed gas bubbles under the sample's surface. The gas bubbles released the nitrogen upwards while the local temperature increased during the implantation or during a later heating process. Craters are formed from the bubbles, which were clearly visible on the AFM photographs. Annealing the modified surfaces in a vacuum always changed the surface topography of the sample. The lowest wear rate and the lowest friction coefficient were observed in the
Cr–Ti–N and
Cr–Al–N samples.
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