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Bulk and local magnetic properties were studied in [1 nm B + 1 nm 57 Fe + x nm Ag] 5 , x = 1, 2, 4, 5 and 10, multilayer samples. Although Ag does not mix with either of the other two elements the magnetic properties of the multilayers are strongly influenced by the Ag thickness below x = 5, whereas no such effect is observed above this value. The Mossbauer measurements indicate a complete amorphization of the thin Fe layers in each sample, as a result of intermixing with the B layers. The variation of the magnetic properties is explained by the variation of the average B concentration of the amorphous Fe–B layers, which depends on the thickness of the Ag barrier layers. The magnetization measurements indicate ferromagnetic behaviour of the ultra-thin amorphous layers with the presence of less than 10% superparamagnetic moments for x = 5 and 10. The average B concentration of the amorphous Fe–B alloy, as estimated from the Fe hyperfine fields, is around 40 at%. It is significantly lower than the 60 at% nominal B concentration, suggesting the presence of an unalloyed B layer, as well. This picture is supported by transmission electron microscopy investigations which reveal two amorphous layers of different B concentration in between the crystalline Ag layers.

Multilayers with Ag/Fe/B and Ag/B/Fe layer sequence were studied in order to reveal differences of top and bottom interfaces of Fe. The hyperfine field distribution depends on the layer sequence and the differences could be attributed to a different B concentration distribution at the top and bottom Fe–B interface.

International audience; Genetic factors, specially those related to serotoninergic activities, and childhood maltreatment have both been implicated in suicidal behaviour (SB). However, little attention has been paid to the possible interaction between genes and childhood maltreatment in the comprehension of SB. Brain-derived neurotrophic factor (BDNF) plays an important role in the growth of serotoninergic neurons during childhood and therefore is a good candidate for studies on SB. Moreover, decreased levels of BDNF have been found in the prefrontal cortex of suicide victims. In our study we wanted to see if Val66Met (a BDNF functional single-nucleotide polymorphism) could moderate the effect of childhood maltreatment on the onset, number and violence of SB in a sample of 813 Caucasian suicide attempters. Childhood maltreatment was evaluated using the Childhood Trauma Questionnaire. We used a regression framework to test the interaction between Val66Met and childhood maltreatment. Childhood sexual abuse was associated with violent suicide attempts (SA) in adulthood only among Val/Val individuals and not among Val/Met or Met/Met individuals (P = 0.05). The severity of childhood maltreatment was significantly associated with a higher number of SA and with a younger age at onset of suicide attempt. This result suggests that Val66Met modulates the effect of childhood sexual abuse on the violence of SB. It is proposed that childhood sexual abuse elicits brain structural modifications through BDNF dysfunction and enhances the risk of violent SB in adulthood.

Magnetic multilayers of 57Fe with nominal thickness, T nom, between 0.4 and 1.0 nm separated by 3.0 nm Al spacer layers were prepared by alternate deposition of the constituents in high vacuum. The samples were investigated at 4.2 K in external magnetic field. A fraction of Fe atoms corresponding to about 0.3 nm equivalent Fe-thickness was found to mix into the Al spacer. The extremely strong magnetic anisotropy observed for T nom

An (0.2 nm 57Fe/2.6 nm Ag)75 granular multilayer sample and heterostructures with additional continuous Fe layers in different sequences were studied in magnetic field applied at different temperatures. The broadening of the superparamagnetic lines was found to be very similar for the three samples in applied fields both parallel and perpendicular to the sample plane. While the layer sequence has no significant effect on the superparamagnetic properties, the continuous magnetic layers follow a different approach to saturation in perpendicular magnetic fields.

The superparamagnetic behaviour of nanocrystalline (nc) Fe80B12Zr7Cu alloys, having different amounts of body centred cubic (bcc) fraction controlled by DSC heat treatments was studied by high temperature SQUID magnetometry and Mossbauer spectroscopy. The granule diameter calculated from magnetic measurements is significantly higher than the X-ray determined grain size but is proportional to that value. The superparamagnetic behaviour is observed at substantially lower temperatures by the Mossbauer spectroscopy than by the macroscopic magnetisation studies, which means that the applied magnetic field significantly influences the superparamagnetic behaviour. © 2003 Elsevier B.V. All rights reserved.

Summary form only given. Soft magnetic nanocrystalline alloy microstructure consists of ferromagnetic crystals with grain sizes in the nanometer range, embedded in a ferromagnetic amorphous matrix. In order to extend the temperature range in which the transition to superparamagnetic behavior can be studied, Fe has been partially substituted by Cr in a Finemet-type alloy. This has the effect of separating the two limiting temperatures for detecting superparamagnetic behavior, the lower being the Curie temperature of the remaining amorphous matrix, and the upper the temperature at which further structural evolution of the nanocrystalline alloy takes place. Hysteresis loops have been measured from 100 K to 700 K.

Magnetoresistance and magnetic behaviour of a vacuum evaporated multilayer consisting of 1.4 nm Fe and 2 nm Ag layers were studied. The magnetisation of the multilayer shows normal ferromagnetic behaviour while the resistance decreases both in parallel and transversal geometry up to 12 T magnetic field and can be well described by squared Langevin functions. The giant magnetoresistance (GMR) is attributed to a small amount of Fe clusters and/or single impurities in the Ag matrix. This explanation is supported by similar results on a 8 nm Ag/25 nm Fe/8 nm Ag trilayer. The concentration distribution due to interface mixing was studied by Rutherford backscattering spectrometry (RBS) measurements.

Anomalous composition dependences of the Curie temperature of the residual amorphous phase in nanocrystalline Fe 92-x B x Zr 7 Cu 1 (2 < x < 23) alloys were studied by Mossbauer and magnetization measurements. The observed large (almost 300 K) increase with respect to that of the precursor amorphous phase at low B content is attributed to the volume effect. Mossbauer line broadening shows the presence of superparamagnetic relaxation of the bcc magnetization in nanocrystalline Fe 74 B 18 Zr 7 Cu 1 well below the Curie temperature of the residual amorphous phase suggesting that interphase exchange coupling is weaker than the dipolar magnetic fields.

Temperature dependence of the magnetic properties of Fe/Ag vacuum evaporated multilayers was studied in a wide range of layer thickness. For Fe thickness larger than 1 nm continuous magnetic layers can be found, but its hyperfine field is significantly lower than that of pure α-Fe at elevated temperatures. It is attributed to a decrease of the Curie temperature due to Ag impurities in the Fe layer. Below 1 nm Fe thickness magnetic relaxation and the formation of a granular alloy with 35 T average hyperfine field was observed. Magnetoresistance results indicate the presence of Fe clusters in the Ag matrix, as well.

Nanocrystalline Fe80Zr7B12Cu1 alloys with different amounts and sizes of bcc precipitates were prepared by appropriate annealing of amorphous ribbons. The 6–10 nm ferromagnetic bcc granules are embedded in a residual amorphous tissue with a thickness at least 4 nm. Above room temperature superparamagnetic relaxation characteristic for small magnetic particles was observed with increasing temperature, as indicated by a significant increase in the width of the Mossbauer lines belonging to the bcc precipitates. It shows the absence of magnetic coupling which is stronger than the dipole-dipole interaction between the ferromagnetic nanoparticles.

The electronic, thermodynamical, and transport properties of ordered ${\mathrm{Fe}}_{3}X$ ($X=\text{Al},\mathrm{Si}$) alloys are studied from first principles. We present here a unified approach to the phase stability, the estimate of the Curie temperature, the temperature dependence of sublattice magnetizations, magnon spectra, the spin-stiffnesses, and residual resistivities. An important feature of the present study is that all calculated physical properties are determined in the framework of the same first-principles electronic structure model combined with the effective Ising and Heisenberg Hamiltonians used for study of the thermodynamical properties of alloys. Curie temperatures, spin-stiffnesses, and magnon spectra are determined using the same calculated exchange integrals. Finally, the transport properties are calculated using the linear-response theory. Our theoretical estimates compare well with available experimental data. In particular, calculations predict (in agreement with experiment) the ordered $D{0}_{3}$ phase as the ground-state alloy structure, demonstrate that a correct relation of Curie temperatures of ${\mathrm{Fe}}_{3}\mathrm{Al}/{\mathrm{Fe}}_{3}\mathrm{Si}$ alloys can be obtained only by going beyond a simple mean-field approximation, provide reasonable estimates of spin-stiffnesses, and give resistivities compatible with structural disorder observed in the experiment. Although the calculated temperature dependences of the Fe magnetization on different sublattices are similar, they nevertheless deviate more than in the experiment, and we discuss a possible origin.

Melt-quenched amorphous Fe 92− x B x Zr 7 Cu 1 (2⩽ x ⩽23) ribbons were heat treated to the end of the first crystallization stage. The size of the BCC grains decreases from 20 to 6 nm with increasing B content, while the average thickness of the residual amorphous phase stays approximately constant at about 4 nm. The nanocrystalline BCC phase contains 2–4 at% of dissolved B and Zr, which is also reflected in its modified Curie temperature. The average composition of the residual amorphous regions in the nanocrystalline composite was established as Fe 2 (B 1− y Zr y ), which makes possible a direct comparison of macro- and nanophases of close composition.

The hyperfine parameters of iron atoms are studied in iron nanocrystallites prepared by different methods: ball milling of iron powder, partial crystallization of Fe-Zr-B-Cu amorphous ribbons, and vacuum evaporation of Fe-B polycrystalline multilayers. Careful analysis of the spectral contribution of the possible impurities and chemical mixing at interfaces reveals that no specific grain boundary contribution can be separated in the M\"ossbauer spectra when the grain size is in the 2--10 nm range. The results indicate that excluding chemical effects the hyperfine fields of iron atoms at the bcc interfaces are very close to those in the bulk, and M\"ossbauer spectra of the iron nanocrystallites studied can be understood without supposing a separate grain boundary phase with very distorted structure or highly reduced density.

The structure and magnetic properties of soft magnetic nanocrystalline composites crystallised from amorphous ribbons are reviewed. The Fe-Early Transition Metal-Boron (Nanoperm-type) nanostructures are discussed in details and compared to the Si containing (Finemet) alloys. The nanocrystallization process was studied by calorimetry; the spatial dimension, the composition and the relative fraction of the bcc and the residual amorphous phases were investigated by X-ray diffraction and Mossbauer spectroscopy. A small fraction of Fe atoms (about 4%) was found which cannot be assigned either to the residual amorphous or to the bcc phase. It is suggested that the magnetic anisotropy of the bcc phase is decreased due to the dissolved Zr and B impurities. The Curie point and Fe atomic moments in the residual amorphous tissue are determined and compared to that of a macrosized amorphous phase of similar composition. The observed deviations do not scale with the average characteristic size of the amorphous phase and thus cannot be explained in the framework of the existing models. Magnetic dipolar coupling and tensile stresses between the grains of the different phases are suggested for explaining the soft magnetic behaviour of the nanostructures.

Iron nanocrystallites of ball-milled iron powder, partially crystallized melt quenched amorphous alloys and polycrystalline multilayers were studied. The change in the hyperfine field at iron atoms due to grain boundaries does not exceed the experimental linewidth.

A discontinuous Fe/Ag multilayer and a granular alloy, both with the overall nominal composition of Fe 10 Ag 90 , were studied by bulk magnetization and Mossbauer spectroscopy measurements. The superparamagnetic blocking temperatures, as measured by the low-field susceptibility, agree quite well but the external-field dependence of the magnetization shows large difference for the two samples at all temperatures and the grain sizes obtained from a Langevin fit to the bulk magnetization differ in almost a factor of two. The discrepancy is attributed to the different directions of anisotropy in the samples, as observed by Mossbauer measurements as well as by comparison of the magnetizations measured in parallel and perpendicular applied fields. Similar grain size is obtained for the two samples by both techniques when a simple large-field approximation ( M ( H ) ∼ M (∞)(1 − kT / μH )) is applied in the calculations.

In this study we have examined the relationship of benzo[a]pyrene (B[a]P) exposure with B[a]P-7,8-diol-9,10-epoxide (BPDE) adduct formation in globin and serum albumin (SA). We also have evaluated the relationship of BPDE-globin and -SA adduct formation with urinary 1-hydroxypyrene (1-OH-pyrene), and bulky DNA adducts in peripheral blood lymphocytes. The study groups consist of male Hungarian garage mechanics (smokers and nonsmokers) exposed to diesel engine exhaust and matched control samples from a blood bank in Budapest. The mean level of BPDE-globin adducts in the garage mechanics (n=15) is 5.9±4.8 fmol/mg globin (ranging from 0.5 to 19.9 fmol/mg globin) and that in controls (n=15), is 2.4±2.5 fmol/mg globin (ranging from ND to 8.5 fmol BPDE/mg globin). The mean of BPDE-SA in garage mechanics is 0.36±0.6 fmol/mg SA (ranging from ND to 2.6 fmol/mg SA) and, in controls it is 0.29±0.3 fmol/mg SA (ranging from ND to 1.3 fmol/mg SA). The results of this study indicate that levels of BPDE-SA adduct...

The composition dependence of the Curie temperature and the magnetic moment of the nano-size residual amorphous phase in partially crystallized Fe92-xZr7BxCu1 (2 x 23) amorphous alloys were determined by 57Fe M?ssbauer spectroscopy. Both quantities show broad minima and for increasing relative Zr content (i.e. for decreasing B concentration) surpass the usual monotonic decrease observed for the bulk counterparts. The deviation does not scale with the characteristic size of the residual amorphous regions, which was found to be constant, ruling out explanations based on interphase exchange interaction. A magnetovolume origin of the observed anomalous composition dependence and the improved soft-magnetic characteristics of these nanocrystals is proposed.

Amorphous Fe2(B1-yZry) alloys, which are important as the residual amorphous matrices in nanocrystalline Fe - Zr - B - Cu systems, were prepared by rapid quenching from the melt for . The iron magnetic moment determined by 57Fe Mossbauer spectroscopy and magnetic measurements shows an unexpected initial increase when Zr is substituted for B. This behaviour, together with the uncommon crystallization sequence, is attributed to the highly attractive B - Zr interaction.

The magnetic behaviour of nanosize ferromagnetic bcc granules embedded in an amorphous tissue (i.e., partially crystallized amorphous alloy) was studied by Mossbauer spectroscopy. The results are compared with the bulk counterparts: bcc-Fe and amorphous . Size dependent enhancement of the Curie point of the nanosize amorphous phase was not observed. At temperatures well above the Curie point of the amorphous phase superparamagnetic relaxation of the bcc crystallites is observed opening new possibilities to study the anisotropy energy of nanosize ferromagnetic grains.

The direction of the spontaneous magnetization changes from out of plane to in plane at around x= 0.6 in [Ag(2.6 nm)/ Fe(x nm)] 10 multilayers (0.2 ≤ x ≤1) prepared on Si(1 11) substrate by vacuum evaporation. Transmission Mossbauer spectroscopy measurements of removed samples with a thick capping layer are compared to conversion electron Mossbauer spectroscopy measurements of samples on the Si substrate with a thin capping layer. The stress arising because of the application of a thick capping layer and the removal of the samples from the substrate is shown to have negligible effect on the spontaneous magnetization. The results support that the appearance of the perpendicular anisotropy below x = 0.6 is an intrinsic property of Fe/Ag multilayers.

The magnetic coupling between nanosize ferromagnetic bcc crystalline grains embedded in a residual amorphous matrix was studied by Mossbauer spectroscopy in nanocrystalline Fe - Zr - B - Cu alloys studied above the Curie temperature of the amorphous phase. It is shown that the ferromagnetic coupling is mediated via an about two atomic layer thick interface region between the nanocrystallites.

Melt spun amorphous Fe 83 B 17 ribbons were pulverized in a planetary ball mill. Two parallel sets of experiment were made, where the material of the vial made the only difference in the experimental conditions. In the first kind of experiments tungsten carbide balls and vials were used, while in the second series the tungsten carbide balls were put in chrome steel vials. This way the effect of impurities on the mechanically induced crystallization could be studied and distinguished from other possible effects. Changes of the amorphous phase and the appearance of crystalline phases were followed by Mossbauer spectroscopy and DSC measurements. The results indicate that contamination from the milling tools causes a shift of the chemical composition of the milled amorphous material. In the case of steel milling tools the appearance of bcc nuclei initiate crystallization during milling. Instead of this bcc structure, a modified amorphous phase with a broader hyperfine field distribution - attributed to the significant amount of dissolved tungsten-- is observed when the amorphous alloy is milled with tungsten carbide balls and vials.. The differences detected under experimental conditions where only the material of the vial was different confirm that the specific impurities introduced in the milling process play a decisive role in the crystallization of amorphous alloys under ball-milling conditions.

The Mossbauer spectra of nanocrystallized amorphous Fe-Zr based alloys are compared to those of melt-quenched microcrystalline Fe-Zr solid solution in the 4-800 K temperature and in the 0-7 T external magnetic field range. It is established for both cases that besides the well known sharp sextet of the bcc Fe phase (main line) and the broad spectrum component a satellite is also observed. Its hyperfine field shows the same temperature and external magnetic field dependence as that of the bcc structure. The results together with high precision X-ray data for the grain size and lattice parameter as a function of the nanocrystallization temperature make it possible to identify that the satellite is caused by (mainly) Zr dissolved in the bcc structure. Our results do not support the idea that the satellite structure is due to a separate interfacial phase.

Magnetic systems with a considerable amount of irregular interfaces were investigated by 57Fe Mossbauer spectroscopy. Chemically homogeneous ferromagnets around the percolation threshold composition of disappearing magnetism and chemically heterogeneous alloys prepared by nanocrystallization of amorphous alloys belong to this class of materials. Low temperature and high field measurements were performed on nanocrystalline FeZrBCu alloys, on ball‐milled Fe with nano‐size grains and on melt‐quenched amorphous Fe–Zr and Fe–Y alloys in order to clarify the origin of large high‐field susceptibility and to investigate the common features of the approach to magnetic saturation. Curie point determination of the residual amorphous phase in the nanocrystalline FeZrBCu alloys, results on the structure of the nanocrystalline b.c.c. phase and of the interfacial region will be reported.

The appearance of bcc Fe after grinding Fe{sub 2}B for a long time has been formerly interpreted as being due to the decomposition of the thermodynamically stable intermetallic compound when the crystallite size is reduced to a few nanometers. The results of our control experiments performed by tungsten-carbide milling tools show that the appearance of bcc Fe has no relation to the grain size but should be connected to contamination when tools made of steel are used to pulverize this material. M{umlt o}ssbauer spectroscopy was applied to search for the appearance of bcc Fe while changes in the grain size were checked by x-ray diffraction and transmission electron microscopy. {copyright} {ital 1998} {ital The American Physical Society}

A combined magnetic, neutron diffraction and field-dependent 57 Fe Mossbauer study of Sc-substituted Ba-hexaferrite in powder form is reported, and the findings are compared with the data for BaFe 12 O 19 . The five cation sublattice with collinear ferrimagnetic structure of uniaxial (Gorter) type for BaFe 12 O 19 , persists also for BaFe 10.4 Sc 1.6 O 19 at room temperature and below down to 130–190 K, depending on the applied field. Below room temperature, BaFe 10.4 Sc 1.6 O 19 undergoes a magnetic transition as indicated by the magnetization and Mossbauer spectroscopic measurements. The neutron diffraction results are compatible with a gradual transformation below 190 K into a complex canted structure with spins pointing out of the axial direction. The complex magnetic order at 10 K can be described in terms of an incommensurate complex block-type conical structure.

Magnetic viscosity was measured for amorphous Fe100 x Zrx (76 x 6 12) alloys in the spin-glass state as a function of magnetic field (0

Mechanical milling of crystalline compounds and mechanical alloying of elemental components yield different products in the case of the Fe - B system. FeB and cannot be amorphized by mechanical grinding. The appearance of the bcc Fe phase during mechanical milling of is due not to decomposition into elemental components, but to contamination from the milling tools. When the stoichiometry is changed, either by contamination during mechanical milling or by mechanical alloying of Fe+FeB or Fe+ powder mixture, an amorphous alloy is formed with composition close to .

The interface of Fe-B multilayers was studied by Mossbauer spectroscopy, X-ray diffraction and transmission electron microscopy. The interface region is amorphous and consumes 2n mfrom the iron layer. The same hyperfine field distribution is observed within the amorphous interface when the individual layer thicknesses exceed the width of the inter- face. The width of this distribution is much larger than those measured in amorphous Fe-B alloys and the excess width is attributed to concentration distribution along the interface. On the contrary, the amorphous component in samples with smaller layer thicknesses is more homogeneous as deduced from the hyperfine field distributions, and the hyperfine pa- rameters depend on the ratio of the iron and boron layer thicknesses. Solid state amorphization during the sample de- position is assumed to account for this behavior. Diffusion amorphization is also detected when low-temperature heat treatment of the large layer thickness samples is performed. Single-phase amorphous alloy is formed in both cases in a limited concentration range around 40 at% boron in agree- ment with the predictions of free-energy diagrams.

After establishing the formula of information, we turn to two cases: to the independent case and to the dependent case. If the characteristics of the particles (e.g., the energy) as random variables are independent, we come in the discrete case to the Boltzmann distribution, while in the continuous case we come to the Gibbs formula-irrespectively of whether the particles are distinguishable or not. Our effort is nimed at clarity of the ideas, not at their mathematical completeness.

Steroid ketoximes were reduced with sodium tetrahydroborate in the presence of nickel chloride or molybdenum trioxide. These processes yielded 17α- and 20α-aminosteroids (1c–5c) in higher yields than common reduction methods.

Nanocrystalline Fe 90 Zr 7 B 2 Cu 1 with ferromagnetic BCC nanocrystals of about 10 -20 nm size embedded in a residual amorphous matrix was produced from amorphous precursor by partial crystallization. A significant increase in the Curie temperature of the residual amorphous phase (T C ) as compared to that of the amorphous precursor was found by combined bulk magnetic and Mossbauer measurements. The unusual increase of T C for alloys with different nanocrystalline fractions correlates with the quantity of the BCC phase.

Equiatomic composition powder mixture of pure Fe and B was mechanically alloyed in a controlled atmosphere vibration mill. Amorphous alloy phase formation was established by Mossbauer spectroscopy and by transmission electron microscopy. The variation of the average boron concentration and the homogeneity of the amorphous phase during the alloying process was followed by Mossbauer spectroscopy. At the early stage of the milling process a broad concentration distribution (from 20 to 50 at. % B) was observed. Upon further milling the average B concentration of the amorphous component was gradually enhanced and the concentration heterogeneity decreased. The B concentration of the amorphous phase could be further enhanced by heat treating the milled powder mixture. The highest boron content alloy attained in this study is Fe60B40.

Solid state amorphization of vacuum evaporated multilayers (ML) were examined on samples with an overalI composition Fe45B55 and Fe layer thickness ranging from 1.5 to 10 nm. The samples were examined by parallel beam X-ray diffraction and by Mossbauer spectroscopy (MS). A 3 nm thick amorphous interface is observed in the as-received samples independently from the thickness of the bee-Fe layer. MS results indicate a broad concentration distribution in this amorphous interface. The thickness of the amorphous layer can be increased by heat treatments below 600 K at least up to 6 nm. INTRODUCTION Although solid state amorphization in the Fe-B system by mechanical alloying was reported by several groups [1,2,3,4] the diffusion amorphization of ML samples seemed to be unsuccessful according to the very few published results [5,6]. In order to investigate the details of the diffusion process and the propelties of the interface between the layers we prepared a series of samples with different Fe layer thicknesses starting from 1.5 run. The Fe-B system is a very well known model system of studies on amorphous alloys and amorphous phase formation by rapid quenching from the liquid as well as crystallization properties are extensi vely studied [7]. The amorphous phase can be prepared in a wide concentration range (from 12 to 90 at% B) by vacuum coevaporation or sputtering. There are only a few crystalline phases (FeB, Fe2B and Fe3B) which cannot support appreciable off-stochiometry. The MS parameters -isomer shift (IS), quadrupole splitting (QS) and hyperfine field (HF)strongly depend on the B concentration of the amorphous phase [8,9] and this way they make possible a consistent estimation of the unknown composition. All these properties make it an ideal system to study the validity of free energy considerations in predicting the concentration range of amorphous phase formation by solid state diffusion. This was calculated to be 32-47 at % B for the Fe-B system [10]. EXPERIMENTAL Multilayered samples with an overall composition Fe45B55 were evapntated either to aluminium foil or Si single crystal substrate in a vacuum of 10-7 Pa with an evaporation rate approx. 0.1 nm/s. The sample holder was cooled by liquid nitrogen during evaporation. The substrate was first covered with 30 nm boron to prevent contamination from the substrate and the topmost layer was boron, as well, of 5 11m width. Samples with 1.5, 2.5, 3.5 and 10 nm Fe layer thickness were prepared with appropriate B layer thickness to get an Fe45B55 overall composition. The layer thickness was controlled by a quartz oscillator. Due to the geometry of the evaporation chamber there is a O. I nm variation of the layer thickness within the sample. The total thickness of the samples was about 200 nm. Heat treatments were also made in the high vacuum evaporation chamber. Parallel beam X-ray diffraction was carried out at the Brookhaven National Synchrotron Light Source X3B I beam line. The 0.11467 nm wavelength was selected by a Si (lll) channel cut monochromator. The sample was mounted on a two circle goniometer. The diffracted beam was detected by a scintillation counter after a Ge single crystal analyzer. This arrangement allowed measurements from 0.8 degree with a 0.002 degree resolution. Fe57 Mossbauer spectroscopy (MS) was made on a standard constant acceleration spectrometer. Samples on the Al substrate were folded up and were measured in transmission geometry whereas samples evaporated on Si single crystal were measured by conversion electron Mossbauer spectroscopy (CEMS). The 776 Mechanically Alloyed and Nanocrystalline Materials helium temperature measurements were made on the Al substrate samples in a Janis cryostat equipped with a superconducting magnet. RESULTS and DISCUSSION The quality of the evaporated multilayers was checked on a few selected samples by X-ray diffraction at small angles corresponding to the layer periodicity. Fig. 1 shows that the multilayer periodicities Fig. 2. Samples on Al substrate had broader diffraction peaks than those on Si substrate. The coherence length calculated from the width of the diffraction peaks ranged from 40 to 75 nm in case of the samples on Al substrates. Side peaks originating from the total thickness of the samples appeared only in case of the samples evaporated on the Si substrate and the separation of these peaks agrees with the 200 nm total thickness.

Low-temperature spin freezing was observed below 25 K in the nanocrystalline (nc)-Fe92−xZr7BxCu1 (x=2–21 at%) alloys prepared from their amorphous precursors by various heat treatments. The freezing causes magnetic hardening with increasing B concentration and annealing temperature, shown by the temperature dependence of both the susceptibility and coercive field. The phenomenon is attributed to the gradual magnetic blocking of a fraction of nanocrystals decoupled from the ferromagnetic matrix. Similar effects are observed in a Cr-containing FINEMET-type nc alloy.

The temperature dependence of the iron hyperfine field distribution is reported in melt-quenched amorphous Fe-Zr alloys. The most remarkable feature is the compositinal change in the shape of the average hyperfine field versus temperature curves. The unusual increase in the average hyperfine field below about 85 K is a characteristic feature of the RSG systems; however, no anomaly is observed in the width of the hyperfine field distribution as a function of temperature. The results cannot be properly explained in the framework of the existing spin glass models.

X-ray diffraction reveals the loss of sharp crystalline peaks, and differential scanning calorimetry shows nucleation controlled transformation besides grain growth in mechanically ground FeB intermetallic compound. On the other hand, the Mossbauer hyperfine parameters are close to the values of the disordered intermetallic compound (α-FeB) and different from those of the amorphous FeB produced by sputtering or evaporation. This controversy is attributed to the disordered interfacial phase existing at the grain boundaries.

Nanocrystalline (Fe1−xCox)90Zr7B2Cu1 (0⩽x⩽0.6) alloys were investigated by x-ray diffraction, 57Fe Mossbauer spectroscopy, and magnetic measurements. The grain size did not change significantly with composition. Co was preferentially partitioned to the residual amorphous phase, and the bcc grains were accordingly enriched by Fe. The room-temperature coercive field increased with the Co addition, which is attributed to the increasing magnetostriction constant.

A new procedure is described for the detection of the acidic metabolites of cortisol (cortoic acids) as the pyrenylmethyl-21-oic esters. The derivatizing reagent, diazomethylpyrene, was prepared by an improved procedure. The reagent was used at room temperature, required no catalyst, and was not restricted by stoichiometric requirements. The steroid esters were separated by reversed-phase high-performance liquid chromatography and analyzed simultaneously by their ultraviolet absorbance and fluorescence characteristics. Identities of the products were confirmed using the photodiode array detector to determine spectral profiles, absorbance maxima, and absorbance ratios. Further confirmation of identity of the cortoic acid esters used mass spectrometry under normal and collision-activated dissociation conditions. With the method described, a linear spectral response was obtained between 8 and 1680 fmol. Application of the technique to the analysis of steroid acids in human urine indicated the presence of cortoic acids.

The temperature dependence of the width of the hyperfine field (i.e. magnetic moment) distribution of crystalline Fe 3 B and FeB amorphous alloys with B composition ranging from 12 to 25 at. % B content is investigated. Qualitative differences are observed and explained within the framework of a model which takes into account the correlations between the magnetic moment and exchange interactions distributions.

Supersaturated Cu 80 Fe 10 Co 10 alloy with a grain size of about 20 nm confirmed by X-ray diffraction was prepared by mechanical alloying from Cu, Fe and Co (−80 mesh, 99.9%) powders. Both room temperature field-dependent and temperature-dependent (FC and ZFC) DC magnetization data, and temperature-dependent AC susceptibility data measured at various frequencies hint at the simultaneous presence of ferromagnetic and superparamagnetic clusters in this alloy. Room temperature Mossbauer results suggest that the Fe atoms are located in a paramagnetic environment, thus the magnetic clusters should be composed mainly of Co atoms.