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Electron paramagnetic resonance (EPR) spectra of manganese-doped strontium titanate were investigated for several Mn concentrations. The spectra of Mn2+ and Mn4+ ions were observed and attributed, respectively, to Mn ions occupying Sr2+ and Ti4+ sites. The relative intensity of the spectra suggested that the manganese ions occupy preferentially Ti4+ sites. The results showed that the EPR peak-to-peak linewidth of the Mn4+ spectrum increases with manganese concentration according to the theoretical equation DHpp=0.45+210.f.(1-f)80 (mT). This suggested that the exchange interaction between tetravalent manganese ions in strontium titanate has an approximate range of 0.96 nm, comparable to that of Gd3+ in the same compound. Resumo Espectros de ressonância paramagnética eletrônica de titanato de estrôncio dopado com manganês foram investigados para várias concentrações de Mn. Os espectros dos íons de Mn2+ e Mn4+ foram observados e atribuídos, respectivamente, a íons de Mn ocupando sítios do Sr2+ e do Ti4+. A intensidade relativa dos dois espectros sugeriu que os íons de manganês ocupam preferencialmente os sítios do Ti4+. Os resultados mostraram que a largura de linha pico a pico do espectro do Mn4+ aumenta com a concentração de manganês de acordo com a equação teórica ΔHpp=0,45+210.f.(1-f)80 (mT). Isto sugeriu que a interação de câmbio entre íons de manganês tetravalente tem um alcance aproximado de 0,96 nm, comparável ao do Gd3+ no mesmo composto.

Nanosized particles of CoAlxFe2-xO4, where 0 ≤ x ≤ 2, were synthesized by the sol–gel combustion method and the magnetic properties of these compounds were investigated. According to X-ray diffractograms, the samples are single phase and the crystallite size is between 7 and 25 nm. The room temperature saturation magnetization of the samples was estimated from the cation distribution and ferromagnetic resonance spectra were used to determine the magnetocrystalline anisotropy. The results show that the saturation magnetization and the magnetocrystalline anisotropy vary over a wide range, from maxima of Ms = 0.42 MA/m and K = 0.39 kJ/m3 for x = 1.0 to minima of almost zero for x ≈ 1.4, a result that could be useful for practical applications of these materials.

A nanostructured GeSb4Te7 (GST147) phase was produced by mechanical alloying (MA), starting from a mixture with nominal GeSb2Te4 composition of high-purity elemental Ge, Sb and Te powders. The effect of milling on z-coordinates of Wyckoff sites 2c and 2d occupied by the Sb and Te atoms was studied using an approach combining the Rietveld method and pair distribution function analysis. The thermal stability of GST147 and the Raman active modes of GST147 were investigated. The results of photoacoustic absorption spectroscopy show that the thermal diffusivity of nanostructured GST147 produced by MA is similar that of its bulk counterpart.

The concentration dependence of the electron spin resonance (ESR) linewidth of Cr3+ ions in chromium-doped barium titanate (BaTiO3) was investigated at room temperature for chromium concentrations between 0.10 and 2.00 mol%. According to previous studies, chromium substitutes Ti4+ sites in the lattice and its preferred valence state is Cr4+, which is ESR silent in the X-band. In the present work, the Cr3+ state was enhanced by codoping with Nb, as it has been done previously in a similar compound, SrTiO3. The results show that the concentration dependence of the ESR peak-to-peak linewidth and the relative intensity of the Cr3+ spectrum can be approximated by the theoretical equations ΔHpp = 3.30 + C1(1 − f)80 mT and I = C2f(1 − f)80, where f is the chromium concentration and C1 and C2 are constants. This suggests that the range of the exchange interaction between Cr3+ ions in barium titanate is about 0.96 nm.

Over the last decades, much research has been done to improve the surface quality of dental implants, but there was no change in the materials used to manufacture the implants. The purpose of the present work is to compare the compressive strength and fatigue failure of dental implants made with a new material, nanocrystalline Ti grade 4 fabricated by Equal Channel Angular Pressing (ECAP) (Ti Hard) with a traditional material, microcrystalline Ti grade 4 (Ti G4). Machined screw-shaped implants with three different designs (Easy, Torq and Flash) made with the two materials were subjected to static and dynamic compressive loads. Implants made with Ti Hard showed higher static compressive strength (Easy: 889.9 ± 79.4 N, Flash: 588.9 ± 74.7 N, Torq: 498.3 ± 54.6 N) than implants made with TiG4 (Easy: 776.4 ± 74.5 N, Flash: 308.8 ± 15.2 N, Torq: 410.3 ± 25.2 N) and higher fatigue strength for 5 106 cycles (Easy: 400 N, Flash: 280 N, Torq: 260 N) than implants made with TiG4 (Easy: 300 N, Flash: 200 N, Torq: 200 N). The higher fatigue strength of nanocrystalline Ti G4 is attributed to a delay in crack initiation.

The atomic short range order of a mechanically alloyed amorphous Ni30Nb70 alloy (a-Ni30Nb70) was determined using two total structure factors S(K) derived using anomalous wide angle X-ray scattering (AWAXS) measurements as input data for reverse Monte Carlo (RMC) simulations. The coordination numbers (Nij) and interatomic distances (Rij) for the first neighbors were obtained. The chemical short range order (CSRO) and the chemical medium range order (CMRO) of a-Ni30Nb70 were investigated using the Cowley-Warren parameter αCW. The results suggest a preference for homopolar pairs or clusters in the first and second coordination shells. The angular distribution of bonds between first neighbor atoms is taken as evidence for the presence of distorted polyhedral units with triangular and square faces in the atomic structure of a-Ni30Nb70.

A nanostructured SnSe 2 phase was successfully produced by mechanical alloying. The influence of defect centers on the structural, optical and photoacoustic properties of the alloy was investigated by annealing the as-milled SnSe 2 powder. From optical absorbance and photoacoustic absorption measurements, the energy band gap, E g , and the thermal diffusivity, α, values were determined for as-milled and annealed samples. The thermal conductivity values for the as-milled and annealed samples were estimated by using the α values obtained from the photoacoustic measurements, the density values obtained from the Rietveld refinement of the X-ray diffraction patterns and the specific heat value for the bulk SnSe 2 phase. These values were used to estimate the dimensionless figure of merit ZT . It was evidenced that the ZT parameter of the as-milled nanostructured SnSe 2 sample is almost twice larger than the ZT of the annealed sample.

An amorphous Ti50Ni25Cu25 alloy was produced by 19 h of mechanical alloying. Anomalous wide angle x-ray scattering data were collected at six energies and six total scattering factors were obtained. By considering the data collected at two energies close to the Ni and Cu K edges, two differential anomalous scattering factors about the Ni and Cu atoms were obtained, showing that the chemical environments around these atoms are different. Eight factors were used as input data to the reverse Monte Carlo method used to compute the partial structure factors STi3Ti(K), STi–Cu(K), STi–Ni(K), SCu3Cu(K), SCu–Ni(K) and SNi–Ni(K) and the partial pair distribution functions GTi3Ti(r), GTi–Cu(r), GTi–Ni(r), GCu3Cu(r), GCu–Ni(r) and GNi–Ni(r). From the RMC final atomic configuration and Gij(r) functions, the coordination numbers and interatomic atomic distances for the first neighbors were determined.

A simple model, based on the relative occupancy of tetrahedral and octahedral sites by different cations, is proposed for the magnetocrystalline anisotropy of mixed ferrite nanoparticles. According to this model, the total magnetocrystalline anisotropy is the weighted average of the contributions of the anisotropies of Fe3+ and M2+ ions in A and B sites. The model predictions are confirmed in the case of cobalt-zinc ferrite.

Electron magnetic resonance (EMR) spectra of gadolinium-doped strontium titanate (SrTiO3) have been studied at room temperature for gadolinium concentrations between 0.20 and 1.20 mol%. The results suggest that the Gd3+ ions occupy substitutional sites, replacing the Sr2+ ion, that the electron magnetic resonance linewidth increases with increasing gadolinium concentration and that the range of the exchange interaction between Gd3+ ions is about 0.96 nm, of the same order as that of the same ion in other host lattices, such as ceria (CeO2), quicklime (CaO), strontia (SrO) and zircon (ZrSiO4). The fact that the electron magnetic resonance linewidth of the Gd3+ ion increases, regularly and predictably, with Gd concentration, shows that the Gd3+ ion can be used as a probe to study, rapidly and non-destructively, the crystallinity and degradation of SrTiO3.

Mechanical grinding (MG) was used to produce nanocrystalline silicon and its thermal and transport properties were investigated by photoacoustic absorption spectroscopy (PAS). The experimental results suggest that in as-milled nanocrystalline silicon for 10 h the heat transfer through the crystalline and interfacial components is similar, and after annealed at 470 °C the heat transfer is controlled by crystalline component.

The effect of pressure on mechanically alloyed trigonal nanostructured SnSe2 (n-SnSe2) was studied by in situ angle-dispersive X-ray diffraction up to 25.8 GPa. The pressure dependence of lattice parameters and unit cell volume was investigated. By fitting the lattice parameters and unit cell volume to a third-order Birch–Murnaghan equation of state for several values of the applied pressure, the bulk modulus B0, its first derivative B′, and the linear moduli along the a- and c-axes were determined. The effect of pressure on the z coordinate of site 2d occupied by Se atoms was investigated using pair distribution function analysis. The results were compared with experimental and theoretical studies of SnS2 and SnSe2 reported in the literature.

Nanostructured Sb 2 Te 3 was produced from Sb and Te by mechanical alloying for 3 h. Volume fractions of crystalline and interfacial components of the milled powder were estimated from the X-ray diffraction (XRD) pattern corrected for polarization, re-absorption, and inelastic scattering and converted to electron units using the theoretical value of the mean square scattering factor 〈 f 2 〉 of Sb 2 Te 3 . Annealing showed that the particles are stable up to at least 583 K. The influence of the interfacial component on optical and thermal properties of as-milled and annealed Sb 2 Te 3 was studied through Raman and photoacoustic absorption measurements. The contribution of the interfacial component to the thermal diffusivity of milled Sb 2 Te 3 was investigated assuming that the measured thermal diffusivity can be described as a random mixture of crystalline and interfacial components. The large volume fraction of interfacial component in the milled powder seems to be responsible for a significant increase in thermal diffusivity. After annealing at 583 K the value of thermal diffusivity is much smaller, close to the one reported for bulk Sb 2 Te 3 .

The present work shows the results of kinetic crystallization of the amorphous metallic alloy Fe 73.5 Cu 1 Nb 3 Si 8.5 B 14 by isothermal annealing, measured by ferromagnetic resonance (FRM) and small angle scattering X-ray in situ (SAXS/WAXS), and by non-isothermal annealing treatment, measured by differential scanning calorimetry (DSC). Only one crystalline phase was observed by WAXS and only one peak was observed by DSC. The activation energies, calculated from FMR and DSC data were 287 and 313.4 kJ mol −1 respectively, showing a good correlation between the two experimental techniques, since the difference is within the limits of experimental error. The values calculated for the Avrami exponent were 1.0 (FMR) and 1.4 (DSC). These values correspond to different mechanisms of nucleation and growth; however, the SAXS/WAXS results suggest that the dominant mechanisms are nucleation and growth of crystals from small dimensions.

Electron spin resonance spectra of Cu 2+ in diluted solid solutions of Cu in CeO 2 have been studied at room temperature for Cu concentrations between 0.20 and 0.80 mol%. Isolated Cu 2+ ions were observed, as well as Cu 2+ ions coupled by the exchange interaction. The linewidth and intensity of the line associated with isolated copper ions have a maximum between 0.60 and 0.80 mol%. The results suggest that the solid solution of Cu in CeO 2 exhibits clustering effects, as was also observed in Mn:CeO 2 solid solutions. A theoretical calculation based on this model yields an effective range of the exchange interaction between Cu 2+ ions of 0.38 nm, smaller than that of Mn 2+ ions in the same host lattice.

Crystallization of the amorphous metallic alloy Fe73.5 Cu1Nb3 Si8.5 B14 was investigated by ferromagnetic resonance (FMR), small angle in situ X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). Only one crystalline phase was observed by WAXS and only one peak was observed by DSC. The activation energies, calculated from FMR and DSC data, were 287 kJ.mol-1 and 313.4 kJ.mol-1, respectively. The values calculated for the Avrami exponent were 0.98 (FMR) and 1.4 (DSC). These values correspond to different mechanisms of nucleation and growth; however, the SAXS /WAXS results suggest that the dominant mechanisms are nucleation and growth of crystals from small dimensions.

Electron spin resonance spectra of Mn 2+ in diluted solid solutions of MnO 2 in Y 2 O 3 have been studied at room temperature for Mn concentrations between 0.20 and 2.00 mol%. Isolated Mn 2+ ions in sites with two different symmetries were observed, as well as Mn 2+ ions coupled by the exchange interaction. The relative concentration of isolated to coupled Mn 2+ ions decreases with increasing manganese concentration. The results are consistent with the assumption that the manganese ions occupy preferentially the C 2 symmetry sites. A theoretical calculation based on this model yields an effective range of the exchange interaction between Mn 2+ ions of 0.53 nm, of the same order as that of Mn 2+ ions in CaO.

Ferromagnetic resonance (FMR) experiments were performed as a function of temperature (10–300 K) on γ-Fe 2 O 3 nanoparticles prepared by a sol–gel method. By measuring at several temperatures the relative intensity of the spectrum due to superparamagnetic particles and the anisotropy field of the spectrum due to ferrimagnetic particles, we determined the size distribution of γ-Fe 2 O 3 nanoparticles. It was found to be a log-normal distribution with a most probable diameter D m =8.1 nm and a standard deviation σ =0.25. Transmission electron microscopy measurements performed on the same samples yielded a log–normal distribution with D m =11.2 nm and σ =0.23. The difference is attributed to the existence of a disordered surface layer in the particles.

Electron spin resonance spectra of chromia-yttria solid solutions have been studied at room temperature for Cr concentrations between 0.20 and 2.00 mol%. Isolated Cr 3+ ions in sites with two different symmetries were observed, as well as well as Cr 3+ ions coupled by the exchange interaction. The relative concentration of isolated to coupled Cr 3+ ions decreases with increasing chromium concentration. The results are consistent with the assumption that the chromium ions occupy preferentially the C 2 symmetry sites. A theoretical calculation based on this model yields an effective range of the exchange interaction between Cr 3+ ions of 0.64 nm, of the same order as that of Cr 3+ ions in MgO.

Electron spin resonance spectra of Gd 3+ in diluted solid solutions of Gd 2 O 3 in CeO 2 have been studied at room temperature for Gd concentrations between 0.01 and 1.00 mol%. While in the case of Mn 2+ :CeO 2 samples, both the linewidth and the line intensity go through a maximum between 0.2 and 0.4% Mn and then start to decrease, in the case of Gd 3+ :CeO 2 samples the linewidth and the line intensity increase monotonically with the dopant concentration. This as taken as evidence that in Gd 2 O 3 –CeO 2 diluted solid solutions there are no clustering effects similar to the ones observed in Mn:CeO 2 solid solutions. It is not clear why clustering effects are present in Mn:CeO 2 solid solutions and not in Gd:CeO 2 solid solutions; however, it seems reasonable to assume that this is due to the fact that the ionic radius of Mn 2+ (81 pm) is about 25% smaller that that of Gd 3+ (107.8 pm). In any case, the fact that Gd:CeO 2 solid solutions do not exhibit clustering effects means that ESR linewidth data can be used to estimate the concentration of Gd in CeO 2 samples, as it is possible to do in several solid solutions of paramagnetic ions in ceramic materials. The results also suggest that the range of the exchange interaction between Gd 3+ ions in CeO 2 is about 0.89 nm.

Structural and magnetic properties of Ni81Fe19/Zr multilayers, prepared by DC magnetron sputtering, were studied using X-ray diffraction, ferromagnetic resonance and magnetization. Low-angle X-ray diffraction results are typical of a modulated structure, while high-angle data suggest that the Ni81Fe19 layers can have amorphous or crystalline structure depending on the thickness. Saturation magnetization increases significantly with thickness of the Ni81Fe19 layers, an effect attributed to the increase in the bulk-to-interface ratio. In a sample where the thickness of the Ni81Fe19 layers is 40 A, the FMR spectrum, with the magnetic field perpendicular to the film plane, displays a spin wave feature, with odd and even modes. Two surface modes are also observed, suggesting that unpinning occurs at both interfaces of the Ni81Fe19 layers. For Ni81Fe19 layers thicker than 40 A, FMR and magnetization data show a surface anisotropy constant (KS) of about −0.32 erg/cm2, which is an indication that the magnetic moment in the Ni81Fe19 layers is confined to the film plane.

The crystallization kinetics of the (Fe50Co50)73.5Ag1Nb3Si13.5B9 amorphous alloy was studied using ferromagnetic resonance (FMR) measurements on samples annealed at 693 K for several periods of time and differential scanning calorimetry (DSC) measurements using several heating rates between 5 and 30 K/s. The increase of the FMR linewidth with annealing time is attributed to crystallization. Assuming a linear relation between the linewidth increase and the transformed volume fraction, it is possible to determine the Avrami exponent, n, from the FMR results: n=1.83±0.10. The DSC measurements show two exothermal peaks, suggesting a crystallization process involving more than one phase. The Avrami exponents calculated from the DSC measurements are n=1.80±0.10 for the first peak and n=1.50±0.10 for the second peak; these results are consistent with a diffusion-controlled process with a decreasing nucleation rate for the first peak and with a nucleation rate close to zero for the second peak. There is a reasonable agreement between the FMR results and the DSC results for the first peak. The activation energies are 353.5±2.8 and 424.9±10.2 kJ/mol for the first and second peaks, respectively.

Electron spin resonance spectra of manganese-doped cerium oxide have been studied at room temperature for Ce concentrations between 0.01 and 1.00 mol%. The linewidths and intensities of the lines associated with isolated manganese ions have a maximum between 0.20 and 0.40 mol%. The results suggest that the solid solution of Mn in CeO 2 is not random, but exhibits significant clustering effects.

This paper describes the determination of the local atomic structure of amorphous TM60Ti40 (TM=Fe, Co, Ni) alloys produced by mechanical alloying (MA) technique. The interatomic distances and the coordination numbers for the TM–TM, TM–Ti and Ti–Ti first neighbors were obtained by making the deconvolution of the first atomic shells of the radial distribution functions, which were calculated from the measured X-ray scattering patterns for the three alloys. The deconvolution was possible because the local atomic structures of these alloys can be accurately predicted by the additive hard-sphere (AHS) model. Thus, the number of TM–TM and TM–Ti first neighbors given by the AHS were used in the deconvolution to find the number of minority Ti–Ti pairs. Our results show complete amorphization for the Ni60Ti40 and Co60Ti40 alloys and partial amorphization in the case of the Fe60Ti40 alloy. These results are consistent with the free enthalpies of mixing for these alloys. A chemical short-range order, greater than expected, was found in the Fe60Ti40 alloy and attributed to partial amorphization of the Fe–Ti system by MA.

Electron spin resonance (ESR) spectra of copper-doped calcium oxide have been studied at 77 K for Cu concentrations between 0.01 and 0.20 mol%. The results suggest that the range of the exchange interaction between Cu2+ ions is 0.68 nm.

The crystallization kinetics of the amorphous metallic alloy Fe 81 B 13.5 Si 3.5 C 2 (Metglas 2605SC) was studied using ferromagnetic resonance (FMR) measurements on samples annealed at 693 K for different times, and differential scanning calorimetry (DSC) with several heating rates between 2 and 30 K s −1 . The increase of the FMR linewidth with annealing time is attributed to crystallization. Assuming a linear relation between the linewidth increase and the transformed fraction, a value of 1.20±0.10 was obtained for the Avrami exponent, n . The DSC measurements showed three exothermal peaks, suggesting a crystallization process involving more than one phase. The lower temperature peak, which appears at about 750 K for a heating rate of 2 K min −1 , increases with heating rate and becomes dominant for heating rates greater than about 10 K min −1 . The Avrami exponent calculated from the DSC results for this peak, n =1.24±0.10, agrees with FMR results within experimental error and is consistent with a diffusion-controlled process with a nucleation rate close to zero.

The influence of aging on thermal and structural properties of ball-milled amorphous selenium has been investigated. Differential scanning calorimetry (DSC) spectra suggest that, with aging, part of the amorphous structure formed by chain molecules transforms into another structure consisting of Se8 rings, which is also found in amorphous selenium prepared by rapid quenching or vapor deposition. An attempt to obtain detailed information about this mixed amorphous structure was done by using radial distribution function RDF(r) analysis.

Electron magnetic resonance (EMR) spectra of gadolinium-doped zircon (ZrSiO 4 ) powders have been studied at room temperature for gadolinium concentrations between 0.20 and 1.0 mol%. The results suggest that Gd 3+ ions occupy substitutional sites in the zircon lattice, that the electron magnetic resonance linewidth increases with increasing gadolinium concentration and that the range of the exchange interaction between Gd 3+ ions is about 1.17 nm, larger than that of the same ion in other host lattices, such as ceria (CeO 2 ), strontium oxide (SrO) and calcium oxide (CaO). The fact that the electron magnetic resonance linewidth of the Gd 3+ ion in polycrystalline zircon increases, regularly and predictably, with Gd concentration, shows that the Gd 3+ ion can be used as a probe to study, rapidly and non-destructively, the crystallinity and degradation of ZrSiO 4 .

Electron magnetic resonance spectra of manganese-doped cadmium oxide (CdO) have been studied at room temperature for Mn concentrations between 0.10 and 1.00 mol%. The results suggest that the range of the exchange interaction between Mn 2+ ions is about 0.56 nm.

Electrical resistivity and ferromagnetic measurements were performed on as-received and partially crystallized samples of a commercial metallic glass, Metglas 2605S-3A. As the measurements were performed on the same set of samples, the influence of sample preparation can be discarded and any difference in the results attributed to intrinsic differences between the two methods. The results of the present investigation suggest that both techniques lead essentially to the same results.

Nanocrystalline particles of cobalt ferrite (CoFe2O4) were prepared by a combustion wave method, based on the Self-propagating High temperature Synthesis technique (SHS), using iron nitrate, Fe(NO3)3⋅9H2O, cobalt nitrate, Co(NO3)2⋅6H2O, and glycine, C2H5NO2. The average particle size, determined by means of X-ray diffraction, was found to depend on the glycine–nitrate ratio and varied between 2.7 and 17 nm. By measuring at several temperatures the relative intensity of the Mossbauer spectra due to superparamagnetic particles and to ferrimagnetic particles, we determined the size distribution of the nanoparticles in one of the samples. It was found to be a log-normal distribution with a most probable diameter D m = 1.8 nm and a full width at half-height Δ D = 2.6 nm .

The crystallization kinetics of the amorphous alloy Fe 67 Co 18 B 14 Si 1 (Metglas 2605CO) has been studied using the FMR technique. The Avrami exponent, n , and the effective activation energy, E c , were determined for the primary and polymorphic crystallization stages. The results for the primary stage ( n =1.00, E c =230 kJ mol −1 ) are consistent with diffusion-controlled growth with a nucleation rate close to zero; for the polymorph stage, the results ( n =1.55, E c =365 kJ mol −1 ) are consistent with diffusion-controlled growth with a constant nucleation rate.

Samples of the amorphous metallic alloy Fe 40 Ni 38 Mo 4 B 18 were submitted to na isothermal crystallization treatment at a temperature of 858 K for different times. The kinetics of the crystallization process was measured using ferromagnetic resonance spectroscopy (FRM). The value of the Avrami exponent, n, for the Fe 40 Ni 38 Mo 4 B 18 alloy was found to be 1.10 ± 0.02 and the activation energy for crystallization obtained by differential scanning calorimetry, DSC, has a value of 302 ± 8 kJ.mol -1 . Amorphous and partially crystallized samples were submitted to electrochemical hydrogen permeation tests at 313 K. It was observed that, as the crystalline fraction increases, the apparent diffusivity, D app , decreases from 22 ± 0.4 x 10 -15 to 8.5 ± 0.3 x 10 -15 m 2 .s -1 . The apparent solubility also decreases, from 170 ± 6.0 molH m -3 to 38.3 ± 1.1 molH.m -3 . This suggests that the crystalline phase obtained by heat treatment of the Fe 40 Ni 38 Mo 4 B 18 alloy promotes a reduction in the mobility of the hydrogen atoms and in the number of sites for dissolution.

Amorphous and partially crystallized samples of Ni81P19 were studied via electrochemical permeation tests at 313 K utilizing a 0.1 N NaOH electrolyte. The volume fraction of crystals obtained by an isothermal ageing treatment at 570 K, for different times, was determined from ferromagnetic resonance spectra at room temperature. The apparent hydrogen diffusion coefficient and the hydrogen permeability were found to decrease with increasing crystallized volume fraction, while the hydrogen solubility decreases for short heat treatment times and partially recovers for longer heat treatments.

A Fortran computer program was developed for the simulation of powder ESR spectra with orthorhombic symmetry in PC-486 class computers. The program was used to compute the resonance fields and amplitudes of the powder ESR spectra of paramagnetic impurities with S = 3 2 as functions of the zero-field parameters D and E. The results, which are presented in graphical form, should be useful for the interpretation of powder spectra.

Electron spin resonance spectra of iron-doped calcium oxide have been studied at 77 K for Fe concentrations between 0.01 and 1.00 mol%. The linewidth and intensity of the line associated with the 1/2↔−1/2 transition have a maximum between 0.20 and 0.40 mol%. The results suggest that the solid solution of Fe in CaO is not random, but exhibits significant clustering effects.

The properties of radiation-induced V2+ centers in MgO were investigated using the electron spin resonance (ESR) technique. The experimenta results suggest that the solid solubility limit of V3+ in magnesium oxide is about 0·01 cation % and that the decay of V2+ centers is a thermally activated process that can be attributed to two different first-order processes. A model for the formation and decay of V2+ centers in MgO is proposed.

Electron spin resonance spectra of gadolinium-doped magnesium oxide have been studied at room temperature for Gd concentrations between 0.10 and 1.00 mol%. The results suggest that the range of the exchange interaction between Gd 3+ ions is about 0.60 nm.

Ferromagnetic resonance (FMR) experiments were performed as a function of temperature (18–300 K) on magnesium ferrite nanoparticles precipitated in magnesium oxide, for two different annealing times. By measuring the relative intensities of the spectra due to superparamagnetic particles and the anisotropy field of the spectrum due to ferromagnetic particles, we determined the size distribution of magnesium ferrite particles. The same method can be applied to other systems of interest, such as magnetic fluids and magnetic powders.

Electron magnetic resonance (EMR) spectra of gadolinium-doped lanthanum oxide powders have been studied at room-temperature for Gd concentrations between 0.02 and 2.00 mol.%. The results suggest that Gd3+ ions occupy substitutional sites, that the EMR linewidth and intensity increase with increasing Gd concentration and that the range of the exchange interaction between Gd3+ ions is about 0.39 nm, much smaller than that of the same ion in other rare earth oxide.

The crystallization kinetics of the amorphous metallic alloy Fe 86 Cu 1 Zr 7 B 6 was studied using ferromagnetic resonance (FMR) measurements on samples annealed at 673, 683 and 693 K for several periods of time and differential scanning calorimetry (DSC) using several heating rates between 2 and 30 K/s. The increase of the FMR linewidth with annealing time is attributed to crystallization. Assuming a linear relation between the linewidth increase and the transformed fraction, a value of 1.00±0.05 was obtained for the Avrami exponent, n . The DSC measurements showed two exothermal peaks, suggesting a crystallization process involving more than one phase. The Avrami exponent calculated from the DSC results for the first peak, n =1.0±0.1, agrees with FMR results within experimental error and is consistent with a diffusion-controlled process with a nucleation rate close to zero.

An investigation of the giant magnetoimpedance effect (GMI) in pieces of a commercial alloy METGLAS 2705 M is presented. The GMI measurements were carried out in as-quenched and annealed samples. The composition C of the samples was investigated by energy-dispersive X-ray spectrometer (EDS) and ferromagnetic resonance has been measured in the X-band (9.5 GHz). It is found that C departs from the nominal value when the electron beam is swept from the center of the ribbon to the edge. On the other hand, while the annealing increases the GMI it decreases the FMR linewidth. Despite the inhomogeneity in the composition it was also found that the GMI is larger in wider samples.

Electron spin resonance spectra of manganese-doped calcium hydroxide were studied at room temperature for Mn concentrations between 0.01 and 2.00 mol%. The results suggest that the range of the exchange interaction between Mn 2+ ions is about 1.05 nm.

Electron spin resonance spectra of manganese-doped strontium oxide have been studied at room temperature for Mn concentrations between 0.10 and 0.40 mol.%. The results suggest that the range of the exchange interaction between Mn2+ ions is about 0.63 nm.

A thermodynamic analysis of the Cr-Ge system suggested that it was possible to produce a nanostructured Cr3Ge phase by mechanical alloying. The same analysis showed that, due to low activation energies, Cr-poor crystalline and/or amorphous alloy could also be formed. In fact, when the experiment was performed, Cr11Ge19 and amorphous phases were present for small milling times. For milling times larger than 15 h these additional phases decomposed and only the nanostructured Cr3Ge phase remained up to the highest milling time used (32 h). From the differential scanning calorimetry measurements, the Avrami exponent n was obtained, indicating that the nucleation and growth of the nanostructured Cr3Ge phase may be restricted to one or two dimensions, where the Cr and Ge atoms diffuse along the surface and grain boundaries. In addition, contributions from three-dimensional diffusion with a constant nucleation rate may be present. The thermal diffusivity of the nanostructured Cr3Ge phase was determined by photoa...