The microstructure of nanocrystalline Pd was investigated by small angle scattering of neutrons and X-rays. The samples were prepared by compacting small crystallites produced by evaporation and condensation in an inert gas atmosphere. The strong scattering signal is interpreted to arise from crystallites embedded in a matrix of incoherent interfaces. Size distributions were deduced from the scattering curves. They consist of two parts: the crystallite size distribution dictated by the production process, and a structureless contribution due to the correlation in the spatial arrangement of the crystallites. The crystallite size distribution may be described by a log-normal distribution centred at R=2nm. The characteristic form of the correlation contribution arises from the dense packing of non-spherical crystallites. From the scattering cross-section in absolute units the volume fraction vc of crystallites was obtained as vc≈0.3, and the mean atomic density ρi in the interfaces as ρi≈0.52. The change of structural parameters during thermal annealing of the samples was studied. Up to high temperatures an appreciable volume fraction of crystallites with nearly unchanged size remains along with large particles.

A new development in the experimental techniques of atom probe microanalysis is described, which involves the use of a position sensitive detector system. This detector subtends a large solid angle (∼20°) at the specimen, and therefore permits the collection of ions from a substantial fraction of the whole surface area of the emitter. Progressive pulsed field evaporation leads to the construction of a three-dimensional map of the atomic chemistry of the specimen. The new instrument is ideally suited to the investigation of complex, ultrafine microstructures. Applications to the study of age-hardened aluminium alloys and Alnico permanent magnet materials are described.

The vibrational properties of iron particles with nanometer sizes in Fe-SiO2 and Fe-A12O3 granular materials are studied by Mössbauer spectroscopy. The spectra include contributions from metallic Fe atoms at the core of the particles and apparently from surface and oxidized Fe atoms, which are analyzed separately. The temperature dependences of the recoilless fractions are analyzed using the Debye model. The Mossbauer Debye temperature ΘM for metallic Fe is found to decrease dramatically with smaller grain sizes, indicative of a “softening” of the phonon spectrum.

The microstructure of TbFeCo amorphous films deposited by a facing targets type of sputtering (FTS) method varied with the change of deposition rate Rd. The films deposited at Rd of about 100–200 nm/min did not present any distinguishable columnar structure while the ones at Rd of about 50 nm/min revealed obvious columnar structure. The films with columnless structure exhibited Kerr rotation angle θk of 0.37 deg. of which the value was higher than that of the films with columnar structure over the wide range of Th content. The torque measurement implied that the presence of columnar structure was not mainly necessary for the occurrence of large perpendicular magnetic anisotropy. Under satisfactory confinement of plasma during sputtering, the dense, uniform and columnless TbFeCo films can be obtained on plasma-free substrate even at Rd as high as 200 nm/min, without destroying the excellent magnetic properties and magneto-optical characteristics.

Previously, we used Digital Image Processing (DIP) to explore the relationships between the growth morphologies of sputtered two-phase nanostructures and their soft magnetic properties [1]. In this work we extended the application of DIP to analyse the effects of deposition parameters and annealing conditions on their soft magnetic properties including disaccommodation.

Magnetically soft, amorphous Co61B39 thin films, exhibiting a two-phase structure, were deposited by sequentially co-sputtering cobalt and boron. We digitized TEM micrographs of these thin films, prepared under different deposition conditions, and subjected to various post deposition processing. Digital Fourier transforms of the TEM micrographs were studied for evidence that the film anisotropy could be correlated with morphological order arising from long and short range interactions between particles over distances of ≈ 0.2 − 1.0 nm.

Our qualitative studies showed that important changes in soft magnetic properties were associated with changes in the two phase morphologies. We determined, for example, that specific morphological changes were associated with the reduction in the magnetic anisotropy produced by annealing. In general, decreases in anisotropy were associated with increased isotropy in Fourier space. The largest reductions and circular symmetric 2D Fourier transforms were produced by rotating field annealing.

Homogeneous gelled composites of iron and silica containing 5–30 wt. % Fe have been prepared by low temperature polymerization of aqueous solutions of ferric nitrate, tetraethoxysilane, and ethanol (with an HF catalyst). X-ray diffraction data, characterized by the presence of a diffuse scattering peak centered at 20≈24 degrees and the absence of any strong Bragg scattering from the iron-containing regions, indicates that these bulk materials are comprised of nanometer-sized regions of iron compounds embedded in a silica gel matrix. Scanning electron microscopy observations show that this matrix is characterized by the presence of many interconnected pores and that the size of these pores is related to the particle size of the Fe-containing regions. The paramagnetic nature of these materials at room temperature, as well as the small size of the iron-containing regions, is indicated by the appearance in many of the samples of only a high intensity central doublet in the 57Fe M6ssbauer spectra. The Mössbauer effect data demonstrates that the form of the iron can be changed by a subsequent treatment in an atmosphere of ammonia or hydrogen at elevated temperatures: for a 10 wt. % Fe sample treated with ammonia, only a central doublet was observed but with a much larger quadrupole splitting and isomer shift. Both of these subsequently treated materials became superparamagnetic at room temperature. In addition, magnetic susceptibility measurements indicate that the hydrogen treated material becomes a spin glass at low temperatures.

We present the results of a comparison between the magnetic properties of granular Fe–Al2O3 and Fe–SiO2. Granular Fe-SiO2 was found earlier to display an anomalous increase in coercivity which appears to scale with the Fe grain size. The Fe-Al2O3 samples were prepared under similar conditions and their magnetic properties determined. The coercivity in granular Fe-Al2O3 is also seen to increase with increasing grain size, showing that the effect is not unique to the Fe-SiO2 system. A major difference between granular Fe–Al2O3 and Fe–SiO2 is the size of the Fe grains, which are smaller in Al2O3.

The coercivity of granular Fe embedded inside an SiO2 matrix was as high as 3 kOe at 6K, and 1.1 kOe at 300K. In this study, we observed a linear temperature (T) dependence of the coercivity for the samples prepared at a high substrate temperature (773K), and a T1/2 dependence of the coercivity for the sample prepared at a low substrate temperature (473K). This indicates that the microstructures of films prepared at different substrate temperatures are not the same. This phenomenon can be explained if we assume that there are interconnections between particles for the sample prepared at a high substrate temperature. We looked for evidence of interconnections between particles with transmission electron microscopy (TEM).

We present a review of critical phenomena in a variety of nanoscale multilayer materials. Discontinuities of interdiffusitives at low temperatures, “the Supermodulus effect” and the “softening” of elastic constants of fcc-bcc structures, other mechanical properties at critical layer thickness are also presented. Some new calculations of elastic constants of (111) fcc and (110) bcc metallic superlattices show large changes as a function of homogeneous lattice strains. The effect of structural relaxations on a number of electronic and magnetic properties is discussed and a new analytical model is developed to explain the origin of interference effects when interfaces are apart by a few interplanar spacings. This model can predict relaxations at interfaces for a variety of materials including metals, semiconductors and ceramics.

Fe/Ti multilayered films composed of Fe and Ti layers with various thickness ( dFe of 10 ∼ 1000 A and dTi of 10 ∼ 200 A ) have been prepared at Ar gas pressure of 2 mTorr by two pairs of Facing Targets Sputtering apparatus which can deposit very thin and continuous films on plasma-free substrates. The total thickness of Fe layers was 1000 A in all of the specimen films.

The periodic microstructure due to compositional modulation was clearly observed not only in the low angle region of X-ray diffraction diagrams but also in the Auger electron spectroscopic depth profile.

With decreasing dFe from 1000 to 20 A, the diffraction intensity of (110) plane in the Fe bcc phase lowered for dTi of 10∼200 A and its interplanar spacing ( d-spacing ) increased for dTi above 50A. This diffraction peak disappeared with further decreasing d below 15 A. At dFe around 25 A, a different peak appeared at the angle slightly lower than that of Fe(110) peak. The diffraction intensity of (002) plane in the Ti hcp phase increased with decreasing dFe. However, its d-spacing depended little on the dFe and took the same value as that of bulk Ti except for very small dTi.

The net saturation magnetization of Fe layers in all of the specimen films decreased gradually with decreasing dFe from 1000 to 50 A, decreased abruptly with further decreasing dFe and became nearly zero at dFe below 15A.

The films annealed at 200 and 400 °C showed obscure periodic microstructure and had larger d-spacing of ∝ −Fe(110) and smaller saturation magnetization than those of the as-deposited ones.

Electrochemical deposition of artificial compositionally modulated superlattices is described. It is shown that the quality of these alloys is comparable or superior to materials produced by vapor deposition or sputtering. The ambient temperature process described by Yahalom has been modified to include a feedback and control system in order to compensate for natural convective disturbances in the electrolyte. Data is presented for copper-nickel samples of varying wavelengths down to 2 nm which suggests that magnetic properties of thin nickel layers are comparable with bulk nickel. Alloys of other types whose properties can be tailored on a near atomic scale will also be discussed along with potential applications.

Sputtered multilayer samples of W and Cu have been prepared on a variety of substrates with nominal individual layer thicknesses ranging from about 5 to about 100 A. High angle X-Ray Diffraction (XRD) data have been obtained at room temperature on all of these samples. In addition, selected samples have been studied by Transmission Electron Microscopy (TEM) and by low and high angle XRD from room temperature to above the melting point of bulk Cu. XRD and TEM data indicate that the as-deposited multilayer samples are comprised of well-defined individual layers due, in part, to the very small mutual solubility of W and Cu. At high temperatures the existence of low angle scattering peaks as well as satellites about Bragg peaks indicates that the layered structure is not lost. As a result, the W-Cu multilayer system seems to be an interesting candidate for the study of the melting behavior of thin Cu layers.

X-ray diffraction is a useful method to measure the microscopic strain profile in multilayered materials. Depth profiles of strain in the modulation direction are obtained by an iterative fitting of the experimental diffraction pattern with a kinematic model. This approach was used to characterize the coherency strain profile in Au/Ni superlattices.

The accommodation of coherency strain through the superlattice is dependent upon the atomic misfit between the component materials and the thickness of each layer. The depth profile of strain was determined for multilayers with repeat periodicities of 2.92 nm and 4.26 nm. A significant volume fraction of interfaces is present in these nanometric dimensioned laminates.