Hyperfine Magnetic Field Distribution Research Articles

Stimulating the amorphous structure of Fe56Co24Nb4B13Si2Cu1 ferromagnetic alloy by thermal annealing, laser and electron beam irradiation: A Mӧssbauer spectroscopy investigation

This study presents a Mӧssbauer spectroscopy investigation of the Fe56Co24Nb4B13Si2Cu1 amorphous ferromagnetic alloy in the as-quenched state and after thermal annealing, laser and electron beam irradiation. Thermal treatment at temperatures of 450–750° C caused nano, partial and complete crystallization of the alloy system. Crystalline phases such as α-(FeCo), (FeCo)2(BSi) and (FeCo)3(BSi) were identified in the thermally annealed specimens. By analyzing the hyperfine magnetic field distributions, it was shown that continuous wave (cw) CO2 laser irradiation of fresh samples determined a more pronounced in-plane orientation of magnetic moment directions and caused changes in the chemical short-range order in the system with non-zero magnetostriction. For direct comparison, atomic rearrangements were not observed in the Fe68.5Co5Nb3Cu1Si15.5B7 ferromagnetic alloy having a zero magnetostriction constant. Unlike the case of laser annealing, irradiation with 11 GeV electrons of the Fe56Co24Nb4B13Si2Cu1 alloy determined a pronounced out-of-plane magnetic anisotropy and supported the formation of stress centers in the irradiated system. Both laser and electron beam irradiation were found to essentially preserve the amorphous phase of the processed alloy.

Insights into the Role of Defects in Fe2(MoO4)3 Catalysts

The catalytic activity and selectivity of Fe2(MoO4)3 obtained from solid-state synthesis protocols is investigated for the oxidative dehydrogenation (ODH) of ethanol to acetaldehyde. While Fe2(MoO4)3 annealed in a MoO3 atmosphere is found to be inactive, ball-milling of such solid-state synthesis precursors leads to an increase in activity, which cannot be attributed purely to the change in the specific surface area nor to a geometric effect of smaller particles. In a systematic study of the synthesis of Fe2O3-free Fe2(MoO4)3 samples, the correlation of ball-milling time, defect concentration, and catalytic activity is presented. In-depth X-ray diffraction studies, magnetic susceptibility, and 57Fe-Mössbauer spectroscopic measurements disclose characteristic signatures of the defect sites in the solid materials introduced by ball-milling and indicate: (i) MoO3-enriched amorphous layers of variable thickness (shell-like) and (ii) crystalline bulk defects corresponding to a reduction in the molar volume of the solid. The onset of recrystallization processes sets in around 300 °C and is accompanied by an enhanced MoO3 mobility in the particles, which adds to an increase in activity and a decreasing selectivity under catalytic conditions. Accordingly, the defects associated with the decreasing amorphous fraction are converted to crystalline bulk defects, which are monitored by the magnetic hyperfine field distribution of the respective Fe sites. Overall, this study shows the importance of the amorphous layer thickness with a sufficient defect concentration and of the bulk defects’ contribution to the chemical gradients, important for the MoO3 mobility and reduction of the MoO3 loss as a volatile species at the solid/gas phase boundary in ODH catalysis.

Cluster-layered [Fe/Cr]30 structure exhibited Kondo-like effect studied by GISAXS and Mössbauer spectroscopy

Structure and morphology of epitaxial [Fe/Cr]30 multilayers with ultrathin Fe layers (nominally 0.12 nm and 0.08 nm) have been investigated by X-ray reflectivity, synchrotron Mössbauer spectroscopy at low temperature and grazing-incidence small angle X-ray scattering (GISAXS). The films demonstrate Kondo-like behavior of electrical resistivity. The GISAXS patterns reveal their cluster-layered structure. The observed side maxima give the information about the sizes and distances between lateral inhomogeneities. Mössbauer reflectivity spectra measured below the critical angle of the total reflection support the existence of the cluster-layered structure of the samples. Magnetic hyperfine field distributions show that largest number of 57Fe atoms is situated in interfaces of iron clusters and their number increases in the thinnest films.

Characterization of Fe3O4 Nanoparticles for Applications in Catalytic Activity in the Adsorption/Degradation of Methylene Blue and Esterification.

The aim of this study is to evaluate the applicability of the catalytic activity (CA) of the Fe3O4 magnetic system in the adsorption/degradation of methylene blue and esterification. The thermal decomposition method allowed the preparation of Fe3O4 nanoparticles. The crystallites of the Fe3O4 structural phase present an acicular form confirmed by X-ray diffraction. Transmission electron microscopy results identified the acicular shape and agglomeration of the nanoparticles. Mössbauer spectroscopy showed that the spectrum is composed of five components at room temperature, a hyperfine magnetic field distribution (HMFD), two sextets, a doublet, and a singlet. The presence of the HMFD means that a particle size distribution is present. Fluorescence spectroscopy studied the CA of the nanoparticles with methylene blue and found adsorption/degradation properties of the dye. The catalytic activity of the nanoparticles was evaluated in the esterification reaction by comparing the results in the presence and absence of catalyst for the reaction with isobutanol and octanol, where it is observed that the selectivity for the products MIBP and MNOP is favored in the first three hours of reaction.

Mössbauer Spectrometry of Model Binary Fe100−xCrx (1 ≤ x ≤ 50) Alloys

Herein, several ways to evaluate Mössbauer spectra of model binary Fe100−xCrx alloys with chromium content varying in the range from 1 to 50 at% (x = 0.94, 2.2, 4.9, 10.4, 15.4, 22.1, and 52.9) are discussed. For low chromium concentrations (up to 15 at%), the method of binomial distribution of individual sextets is suitable. Depending upon the Cr content, the number of sextets used can be, however, as high as 20. The specific number of sextets is determined according to probabilities of individual atomic sites calculated from binomial distribution. Mössbauer spectra of samples with Cr concentrations higher than 20 at% are evaluated by distributions of hyperfine magnetic fields. The composition of model alloys is verified using X‐ray fluorescence. Their surface is analyzed by two different surface‐sensitive methods: scanning electron microscopy and atomic force microscopy. The main technique used to analyze the materials’ subsurface layers is conversion electron Mössbauer spectroscopy. The applied fitting models and results are useful in studies of the microstructure of real types of construction and stainless steels.

2 GeV Electron Beam Irradiation Effects in Advanced Metallic Glasses

Six amorphous alloys (Alloy 1: Fe56Co24Nb4B13Si2Cu1, Alloy 2: Fe68.5Co5Nb3Cu1Si15.5B7, Alloy 3: Fe75.3Ni0.8Cr0.9Si8.7B14.3, Alloy 4: Fe56Co24Cr10Nb4B3Si1Cu2, Alloy 5: Fe72.9Nb3Cu1Si16.2B6.9, Alloy 6: Fe83.3Si8.6Nb5.5B1.4Cu1.2) were selected in terms of their composition and magnetostriction constants and uniformly irradiated in a high radiation environment in Hall A of the Thomas Jefferson National Accelerator Facility. The 2 GeV electron beam irradiation-induced effects were characterized by Mӧssbauer spectroscopy. The microstructural changes were related to the evolution of the hyperfine magnetic field distributions and isomer shifts. In particular, the occurrence of stress centers in the amorphous materials was evidenced.

The effect of temperature on parameters of hyperfine interactions and spatial spin-modulated structure in multiferroic BiFeO3

A detailed study of the temperature-dependent evolution of the hyperfine interaction parameters and spatial spin-modulated structure in multiferroic BiFeO3 has been carried out by 57Fe Mössbauer spectroscopy in a wide temperature range, including the temperature of the magnetic phase transition. Temperature dependences of the hyperfine magnetic field distributions, isotropic and anisotropic contributions to hyperfine magnetic fields, quadrupole shift and the anharmonicity parameter were measured. A change in the sign of the effective magnetic anisotropy constant was detected at a temperature T ≈ 330 K. At this temperature, the magnetic anisotropy changes from the “easy axis” to the “easy plane” type.

The effects of selenate on goethite synthesis and selenate sorption kinetics onto a goethite surface - A three-step process with an unexpected desorption phase

Iron oxyhydroxides are widely spread in soils and sediments. They can considerably affect the migration of selenate in the environment, due to their high affinity towards oxyanions. To assess the sorptive properties of one of the most common oxyhydroxides, the selenate sorption onto goethite and its effects on goethite's structural properties during its crystallization were investigated. The sorption kinetics of selenate onto goethite at different pH revealed the presence of a desorption phase that had manifested extensively, especially at higher pH values. Also, an isotherm study indicated that the selenate sorption onto goethite is multi-layered at higher concentrations. Phosphate, which is one of the common naturally occurring oxyanions, affected selenate sorption onto goethite significantly, while chloride and sulfate influenced sorption only marginally. The Mössbauer spectrometry showed no structural changes after iron oxyhydroxides crystallization in the presence of selenate. However, changes outside the goethite lattice were manifested by the alterations in distributions of hyperfine magnetic fields obtained from Mössbauer spectra analyses, as well as by the changes in values of the selenate-treated samples' surface charge.

Performance of Maraging Steel Sleeves Produced by SLM with Subsequent Age Hardening.

In the paper, the researches on sleeves made out of maraging steel 1.2709 using selective laser melting (SLM) technology are presented. This additive technology is recognized as favorable for the environment, due to 100% use of material and durability of manufactured details. The fabricated sleeves underwent subsequent tests, in particular, microhardness, porosity and homogeneity of the material was examined before and after heat treatment and salt bath nitrocarburizing process. Two kinds of fatigue tests were performed. The first consisted of the typical sinusoidal alternating load, the other was the high pressure pulse load test close to the real work conditions. It is of high importance that the fatigue strength of the tested sleeves is considerably higher than that of the similarly produced details shaped as a standard samples for tensile stress. The Mössbauer spectrometry analysis of hyperfine magnetic field distributions proved that SLM did not change considerably the martensite structure at atomic level.

Variation of Structural and Hyperfine Parameters of (Fe0.70Al0.30)1-xNbx, with x=0, 0.05, 0.10 and 0.20 System

Fe0.70Al0.30 alloy is a bcc and ferromagnetic phase, being the Al atoms magnetic dilutor. In this work, we study the effect of the Nb on the structural and hyperfine behavior of the Fe0.70Al0.30 alloy when atoms of Nb substitute atoms of Fe or Al. The nanostructured system of (Fe0.70Al0.30)1-xNbx (x = 0, 0.05, 0.10, 0.20, at. %) was obtained by alloying Fe, Al and Nb powders in a planetary ball mill during 12 h, 24 h and 36 h, and a ball mass to powder mass relation of 10:1. The magnetic and hyperfine properties of the samples were studied by X-ray diffraction (XRD) and Mössbauer Spectrometry (MS) at room temperature, respectively. The X-ray diffraction patterns for x=0 showed the bcc-α FeAl structure and its lattice parameter is approximately constant with milling times (∼ 2.91 Å). For x=0.05, 0.10 and 0.20 the patterns showed the coexistence of the α-FeAl, Nb(Fe,Al)2 structural phases with an amorphous component. The Mössbauer spectra of x=0 samples were fitted using hyperfine magnetic field distributions (HMFDs), and the obtained mean hyperfine fields (MHF) were 23.4, 24.2, and 24.3 T for 12, 24, and 36 h of milling time, respectively, which correspond to the α-FeAl structure. The spectra of the samples with x=0.05 and 0.10 were fitted using a model with two components, the first one is a HMFD attributed to the bcc-FeAlNb structure and the second with two doublets attributed to the Nb(Fe,Al)2 structure. When atomic percentage of Nb increases up to 20 at. % the ferromagnetic behavior is diluted due to substitution of Fe-atoms by Nb and Al atoms in the bcc-FeAlNb structure. The magnetic behavior becomes paramagnetic at x=0.20, the spectra were fitted with three doublets, one of them related with bcc-FeAlNb structure and the others to the Nb(Fe,Al)2 structural phase. The alloying of Nb to the Fe0.70Al0.30 system destroyed the magnetism due the substitution of Fe by Nb atoms and generates an amorphization into the system.

Corrosion resistance of AISI 316L plasma nitrided at different temperatures and times

Austenitic stainless steels are widely used as biomaterial and corrosion resistance is one of the most important characteristics in determining the suitability of a material for this purpose. Plasma nitriding is a surface treatment that introduces interstitial nitrogen into these steels, which improves this property as a result of the nitrided layer, whose properties depend strongly on the conditions used in the process. In this paper, the nitriding temperatures (623, 673 and 723 K) and times (3, 4 and 5 h) were investigated. The Mossbauer Spectroscopy was correlated to the corrosion results with the purpose of finding the combination of time and temperature that optimize the corrosion improvement. An alternative method of spectra analysis, which analyzes qualitatively the hyperfine magnetic field distributions, was used and showed that the nitrided layer protects against corrosion, not only because of the expanded austenite, but also, and mainly, because of the nitrides, which are formed therein, located up to a depth of 0.1 μm. Moreover, these results indicate that temperature = 673 K and time = 4 h is the most efficient combination to optimize the corrosion resistance of the samples, nitrided at 6 Torr of the 80% H2–20% N2 gas composition. They also confirm that corrosion protection increases for higher nitriding pressure.

Cluster-glass-like behavior in zinc ferrite nanograins

Structural and magnetic properties of ZnFe2O4 nanograins, prepared by high-energy ball milling and annealed, were systematically studied by X-ray diffraction, 57Fe Mössbauer spectroscopy and AC magnetic susceptibility measurements. Disordered spinel-like structure, with a grain size of 12 nm, is established after 200 h of milling. While the 300 K Mössbauer spectrum of the as-milled sample (200 h) displays broad magnetic absorption lines, characteristic of a disordered system, the magnetization data do not show a magnetic phase transition between 4 and 300 K. At low temperatures, the Mössbauer spectra suggest the presence of two distinct ferrite magnetic phases: one attributed to the grain core (crystalline-like phase), with magnetic ordering temperature of about 90 K, and one showing a magnetic hyperfine field distribution; the latter is associated with a chemically disordered phase (grain boundary contributions). Annealing the 200 h sample at 973 K leads to an improvement of atomic ordering of the spinel structure (reduction of cationic inversion) and average grain size of about 17 nm. AC magnetic susceptibility shows a cusp at about T≈30K, whilst Mössbauer experiments in the same sample reveal magnetic blocking in the same temperature range. The frequency dependence of susceptibility suggests the formation of a cluster-glass-like state. High temperature susceptibility can be described with a Fulcher law of interacting magnetic clusters.

Theoretical and experimental comparative study about magnetic behavior of Fe-Al alloys in the high Fe concentration region

In this research, annealing samples of Fe100-qAlq (with q ≤ 600/32; Δq = 100/32) were obtained by arc-melting. These were heat treated at 1000 °C during a week followed by quenching in ice water. The ferromagnetic iron matrix was modified with the non-magnetic Al atom. These samples were analyzed by X-ray diffraction and Mössbauer spectroscopy at room temperature. All alloys present disordered body centered cubic (BCC) structure or A2 with mean crystallite sizes of about 34 nm. It was observed that when q = 3.125% the iron's hardness falls over 80%. Furthermore, Mössbauer spectroscopy shows that all alloys are disordered and ferromagnetic. The spectra were fitted using a hyperfine magnetic field distribution with ΔH = 1T. Statistical and hyperfine parameters of the distributions were obtained as a function of q. After fixing the Mössbauer spectra, it was found that the mean hyperfine magnetic field (MHMF) presents a linear decrease with the Al concentration. This behavior is strongly related with the diluted character of the impurity. Through Mössbauer spectroscopy and/or X-ray diffraction, an anomalous behavior was observed around q = 12.500. Moreover, by using the Monte Carlo method and the local environment model, the long-range order parameter of the samples was possible to obtain. Additionally, only 2 samples reached the perfect disorder, which indicated that the method of preparation does not guarantee the state of perfect disorder. The local environment model allowed finding the variations in the hyperfine field of the Fe when one atom of Fe is replaced by one Al atom in the first or second coordination shell of the 57Fe. Finally, the Monte Carlo method with Metropolis dynamics and the ½ Ising model were used to simulate the magnetic behavior of the alloys, used in this study. The results were compared with experimental phase diagrams of these alloys, allowing us to find the functionality of the exchange energy in the system as a function of Al concentration. For this system, the phase diagram was fitted using a cubic function of the JFeFe exchange energy with the aluminum concentration.

Comparative study of the mechanical and tribological properties of a Hadfield and a Fermanal steel

In this study, Fe-12.50Mn-1.10C-1.70Cr-0.40Mo-0.40Si-0.50(max)P-0.50(max)S (Hadfield alloy) and Fe-28.4Mn-0.86C-1.63Al-0.42Cu-1.80Mo-1.59Si-0.60W (Fermanal alloy) (Wt. %) in the aged condition were compared in terms of its tribological and microstructural properties. The x-ray diffraction (XRD) patterns were refined with the lines of the austenitic γ-phase, Chromium Iron Carbide (Cr2Fe14C), Iron Carbide (Fe2C), and Iron Oxide (Fe0.974O (II)) for the Hadfield alloy, and the lines of the austenitic γ-phase, martensite (M), Mn1.1Al0.9 phase and iron carbide (Fe7C3) for the Fermanal alloy. Mossbauer spectra were fit with two sites for the Hadfield alloy, which displayed as a broad singlet because of the austenitic disordered phase, and had a magnetic hyperfine field distribution, which corresponds to the Cr2Fe14C ferromagnetic carbides found by XRD. There were two paramagnetic sites, a singlet, which corresponds to the austenite disordered phase, and a doublet, which can be attributed to the Fe7C3 carbide. The obtained Rockwell C hardness for aged Hadfield and Fermanal alloys were 43.786 and 50.018 HRc, respectively.

Mössbauer and XRD characterization of the effect of heat treatment and the tribological test on the physical and mechanical properties of a Fe-Mn-Al-C alloy

In this study, a Fe-29.0Mn-6.0Al–0.9C-1.8Mo-1.6Si-0.4Cu (Wt. %) alloy was prepared in an induction furnace. The as-cast sample was submitted to homogenization at 1050 °C over 8 hours, which was followed by quenching, and an aging heat treatment at 500 °C for 12 h. Wear tests were performed by using a Pin on Disk Tribometer (ASTM G99) at room temperature to evaluate the mass loss. Optical Microscopy, X-Ray Diffraction, and Transmission Mossbauer Spectroscopy were used to characterize the microstructure and structural properties of the samples. The obtained microstructure of the heat-treated samples was of the austenitic type, and their XRD patterns were refined with the lines of the austenite, martensite, galaxite, and FeO structures. Mossbauer spectra of powders, obtained from the surface of the samples, showed the presence of a broad doublet, which corresponded to the disordered austenite; and a small hyperfine magnetic field distribution associated with the disordered and ferromagnetic martensite. After the tribology test, the surface of the sample was examined, and it was obderved that the austenite, martensite, and galaxite phases were present. The martensite quantity increased and, those of galaxite and austenite decreased, but that of austenite appeared to have larger lattice parameter. The decrease in the galaxite content was a direct consequence of the wear test, which removed matter from the sample surface. The appearance of additional martensite was due to the transformation of the austenite by mechanical work. The additional presence of a new austenite with a bigger lattice parameter and of the Fe oxide was the consequence of the heating process of the sample during the tribological test. The Mossbauer spectrum of this sample confirms the increase of the martensite content. The mechanical properties increased with the heat treatment.

Structural and magnetic properties of FeCoC system obtained by mechanical alloying

Fe96−XCoXC4 (x = 0, 10, 20, 30, 40 at. %) alloys were obtained by mechanical alloying of Fe, C and Co powders using high-energy milling. The structural and magnetic properties of the alloy system were analyzed by X-ray diffraction, Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM) and Mossbauer Spectrometry at room temperature. The X-ray diffraction patterns showed a BCC-FeCoC structure phase for all samples, as well as a lattice parameter that slightly decreases with Co content. The saturation magnetization and coercive field were analyzed as a function of Co content. The Mossbauer spectra were fitted with a hyperfine magnetic field distribution showing the ferromagnetic behavior and the disordered character of the samples. The mean hyperfine magnetic field remained nearly constant (358 T) with Co content.

Crystallization Behavior and Recoilless Fraction Determination of Amorphous and Nanocrystalline Fe56Co24Nb4B13Si2Cu1 System

ABSTRACTAmorphous ferromagnetic alloy with the composition Fe56Co24Nb4B13Si2Cu1 was obtained by rapid quenching from the melt. Samples cut from the ribbons were annealed at 450, 550, 650 and 750 °C in a vacuum furnace. 57Fe Mössbauer spectroscopy was used to identify the phases formed based on the refined values of the hyperfine parameters. The as-quenched specimen was analyzed with a hyperfine magnetic field distribution and corresponded to an in-plane orientation of the magnetic moment directions. The sample annealed at 450 °C was found to be in a nanocrystalline state due to observation of the (FeCo)-Si alloy with the DO3 structure. The balance of the composition was represented by a metalloid-enriched amorphous grain boundary phase. In contradistinction to this, the samples annealed at 550-750 °C were totally crystallized and the new phases formed were α-(FeCo), (FeCo)2(BSi) and (FeCo)3(BSi). These findings suggest that nanocrystallization is obtained only at select processing temperatures. A new set of Mössbauer spectra was obtained by recording simultaneously the intensity transmitted by a sandwich of the sample with the stainless steel etalon, based on the dual absorber method recently introduced by us. The values of the recoilless fraction can be derived from the relative spectral areas. The f factor value dropped from 0.6 to 0.37 for the sample annealed at 450 °C, consistent with the onset of nanocrystallization in the system. For the completely crystallized specimens, the f factor maintained values close to 0.5. This indicates that the presence of quenched-in stresses may play a role in the ability of samples to undergo recoilless emission and absorption of gamma rays.

Structure, Magnetic Properties and Hyperfine Parameters of Nd-Substituted Ni-Fe-Ga Heusler Alloys

ABSTRACTSamples of Ni57-xNdxFe18Ga25 with x=2 and 4 were prepared in ribbon form by rapid quenching via melt spinning route. The samples were analyzed by X-ray diffraction (XRD), magnetic measurements and Mössbauer spectroscopy, both in the as-quenched form and after thermal annealing at 900 oC for 2 min and 400 °C for 2 hours. For x=2 the Nd atoms are completely dissolved in the Ni-Fe-Ga matrix, while for x=4 the additional occurrence of the secondary 2:17 phase could be resolved. These findings were supported by the analysis of hyperfine magnetic field distributions obtained from the non-linear least-squares fitting of the Mössbauer spectra.

Effects of relaxation time on local structural and magnetic properties of Fe80.8B10P8Cu1.2 amorphous alloy

Over past decades, Fe-based amorphous and nanocrystalline alloys have aroused a popular research interest because of their ability to achieve high saturation magnetic flux density and low coercivity, but the mechanisms for modifying annealing-induced magnetic properties on an atomic scale in amorphous matrix due to structural relaxation has not been enough understood. In this work, we study the effects of pre-annealing time on local structural and magnetic properties of Fe80.8B10P8Cu1.2 amorphous alloy to explore the mechanisms for structural relaxation, particularly the evolution of chemical short range order. The alloy ribbons, both melt spun and annealed, are characterized by differential scanning calorimetry, X-ray diffractometry, Mössbauer spectroscopy and magnetometry. The magnetic hyperfine field distribution of Mössbauer spectrum is decomposed into four components adopting Gaussian distributions which represent FeB-, Fe3P-, Fe3B- and α-Fe-like atomic arrangements, respectively. The fluctuation of magnetic hyperfine field distribution indicates that accompanied with the aggregation of Fe atoms, the amorphous structures in some atomic regions tend to transform from Fe3B- to FeB-like chemical short-range order with the pre-annealing time increasing, but the amorphous matrix begins to crystallize when the pre-annealing time reaches 25 min. Before crystallization, the spin-exchange interaction between magnetic atoms is strengthened due to the increase of the number of Fe clusters and the structure compaction. Thus, saturation magnetic flux density increases gradually, then shows a drastic rise when there appear α-Fe grains in the amorphous matrix. Coercivity first declines to a minimum after 5 min pre-annealing and then increases drastically. This is attributed to the fact that excess free volume and residual stresses in the melt spun sample are released out during previous pre-annealing, which can weaken magnetic anisotropy significantly, while the subsequent pre-annealing destroys the homogeneity of amorphous matrix, resulting in the increase of magnetic anisotropy. In addition, the separation of Cu atoms from the first near-neighbor shell of Fe atoms and the obvious decrease in the Fe-P coordination number suggest the formation of CuP clusters, which can provide heterogeneous nucleation sites for α-Fe and contribute to the grain refinement. Therefore, through controlling the pre-annealing time, we successfully tune the content values of CuP and Fe clusters in the amorphous matrix to promote the precipitation of α-Fe and refine grains during crystallization. For Fe80.8B10P8Cu1.2 nanocrystalline alloy, an enhancement of soft magnetic properties is achieved by a pre-annealing at 660 K for 5-10 min followed by a subsequent annealing at 750 K for 5 min.

Field-temperature evolution of the magnetic state of [Fe(1.2 Å)/Cr(10.5 Å)]30 structure by Mössbauer reflectometry with synchrotron radiation

Nanostructured epitaxial [57Fe(1.2Å)/Cr(10.5Å)]30 multilayer with ultrathin Fe layers, demonstrated Kondo-like behavior, has been investigated by means of the nuclear resonance reflectivity at low temperatures (down to 4K) in magnetic fields up to 4T. We detected the beginning of the magnetic phase transition at 150K which correlates with the minimum on the electrical resistivity curve. The determined magnetic hyperfine field distribution P(Bhf) indicates an inhomogeneity of the iron environments. When we apply the very high external magnetic field up to 4T, it aligns Bhf(i) along the direction of the external field only partially. Also it has been noticed that Bhf(i) orientations depend on the magnetic pre-history.