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The paper presents the experimental results of rigid-lattice proton magnetic resonance spectra and second moments in Pd–H, Pd 0.90 Ag 0.10 –H, Pd 0.80 Ag 0.20 –H, Pd 0.75 Ag 0.25 –H, and Pd 0.65 Ag 0.35 –H alloys at T = 2.4 K in a wide hydrogen concentration range. Free induction decay (FID), solid and inhomogeneous echoes were detected and interpreted. The interpretation based on dipole–dipole interaction of homogeneously distributed proton spin system is satisfactory at high hydrogen concentration, but an inhomogeneous field of paramagnetic origin (most probably coming from Fe impurities) plays the dominant role at small hydrogen content. An unexpected correlation was found between the macroscopic magnetic susceptibility and the second moment coming from the inhomogeneous internal field.

The fraction of mobile (unfrozen) water during phase transitions of NaCl–H2O solution and tris(hydroxymethyl)aminomethane (Tris) buffer solution has been determined by differential scanning calorimetry (DSC). Measurements were carried out in the temperature range between −50 and +30 ◦ C with a heating rate of 2 K min −1 . The fraction of mobile water was estimated from the enthalpy of melting of the different frozen phases present in aqueous solution samples. Results are supplemented by proton NMR intensity measurements in the same temperature range. A small endothermic peak was detected in the DSC curves at the same temperature where the change in the NMR intensity occurs. We assume that activation/deactivation of rotational molecular motion of hydration water molecules occurs at the steps of the NMR intensity at higher and lower temperatures during heating and cooling, respectively. The rotational motion is probably the initial stage of the eutectic phase separation. Tris additive to NaCl solution causes thermal shifts of the small endothermic peak and in the related NMR intensity. These qualitative differences indicate interactions of Na + and Cl − ions with the small organic molecule constituents.

A systematic NMR study was performed on several alkyl–tetrazole complexes of iron(II) and zinc(II) in the 10–300 K temperature range. The experiments were designed to separate the electronic and reorientational phase transitions caused by the spin crossover of the iron compounds from those independent of unpaired electrons. The 19F spectral data on the propyl-tetrazole compounds show that the electronic spin-transition has a strong effect on the spectra, and their behavior can be explained as a combined response to molecular reorientations and the spin transition. For these complexes, second-moment calculations revealed the strength of the interaction between resonant and nonresonant nuclei. Both of the applied NMR methods show irregularities at the temperature region between 70 and 120 K, suggesting the presence of a phase transition. The data also suggest two kinds of reorientational behavior for the BF4 − counter ions. In the iron–ethyl–tetrazole compound, unlike in the propyl–tetrazole complex, a significant amount of unpaired electrons remains in their original high-temperature HS state. Above their effect, the behavior of the nuclear spins of the iron compound is basically governed by the same structural factors as in its zinc analog. The two-exponential behavior of the 1H-T 1 in case of the zinc–methyl–tetrazole compound can be explained on the basis of cross relaxation with the 19F nuclei due to the low 1H/19F ratio. The presence of the two types of methyl reorientation is assumed to be the sign of the two different lattice sites known to be present in the FeII compound. The single-exponential T 1 above T c in the case of [Fe(mtz)6](BF4)2 is consistently the sign of the strength of the paramagnetic relaxation observed in the ethyl and propyl compounds.

Simultaneous realisation of hydrogen charging or discharging process and in situ measurements of different NMR characteristic quantities give outstanding chances for the investigation and understanding of local physical properties of and hydrogen diffusion in dis- ordered metal-hydrogen systems, including both equilibrium and non-equilibrium states. A few selected preliminary experimental results are presented in this letter for Pd0.9Ag0.1-H al- loy on in situ hydrogen concentration, proton NMR line-shift and magnetic susceptibility, 1 H NMR spectrum, spin-spin relaxation time and hydrogen diffusion activation energy and cor- relation time measurements. The motional averaged spectrum is asymmetric and the possible decompositions relate to the non-single-site residence of hydrogen in this alloy. Introduction. - Feenstra et al. (1) recently proposed to consider hydrogen embedded in a metallic lattice as a "local probe" for the investigation of local properties of hydrogen containing disordered alloys. In this concept Solomons and co-workers (2) used thermodynamic data of hydrogen absorption for Pd-Ag-H alloys and a multi-site lattice-gas model for the determination of site energies of hydrogen located in the centre of Pd1−xAgx octahedron, and the terminology of "hydrogen spectroscopy" was introduced by them. The Pd-Ag alloys are probably the simplest and consequently the best representatives of the chemically disordered alloys, they were subjects of widespread experimental and the- oretical investigations (see, e.g., (3-5) and references therein). The atomic size of the two alloying elements are nearly the same in this system, and Pd and Ag form homogenous solid solution of face-centred-cubic (fcc) structure in the whole concentration range. The hydrogen solubilities for the pure metals differ by many orders of magnitude, so the local distribution of constituents (probably binomial) could strongly affect the microscopic physical properties, too. The magnetic susceptibility of pure Pd is reduced by both silver and hydrogen addition demonstrating the change of the electron structure. The other properties, which are impor- tant in this context, i.e. hydrogen solubility, hydrogen diffusivity, nuclear magnetic relaxation rates, also depend on the composition. NMR —as is well known— is one of the most widely applied local methods, and hydrogen nuclei serve a priori as local probes for the investigation of different microscopic properties

1H NMR spectra of the spin-crossover compound [Fe(ptz)6](BF4)2 and its zinc(II) analogue were recorded on polycrystalline samples as the function of decreasing temperature in order to study the connection of the change in the electronic state and the molecular motions present in both crystals. The temperature range for the zinc compound was 295–30 K, with a cooling rate of ∼1 K min−1, while in the case of the iron(II) compound this temperature range was 298–10 K with the same cooling rate as in the case of [Zn(ptz)6](BF4)2. The analysis of the temperature dependence of the line shape parameters and calculations of 1H second moments showed the following. The temperature of the spin transition in the iron(II) compound is 132 K on cooling. On the basis of the similarity of the temperatures at which the different molecular motions appear, the same motions are present in both compounds in the whole temperature range. The [Zn(ptz)6](BF4)2 probably goes through a structural transition between 90 and 60 K, this transition manifests in the virtual increase of the average proton–proton distance, and the sign of a similar transition is also observed in [Fe(ptz)6](BF4)2.

We have investigated the rotor-stator molecular crystal fullerene-cubane (C 60 .C 8 H 8 ) by 1 H'NMR spectroscopy in the temperature range of 130 to 380 K. The 1 H line is broad and exhibits fine structure characteristic of a multispin spectrum, indicating the absence of angular reorientations of the cubane molecule. The temperature and field dependence of the spin-lattice relaxation rate of cubane protons is well explained in terms of field fluctuations arising from reorientations of the C 60 molecules. Despite the closely packed structure, the activation energy of these reorientations, 650 K, is close to that observed in the high-temperature phase of pure C 60 indicating that the static cubane molecules act as efficient bearing for the rotating fullerene molecules.

A two-exponential spin-lattice ( T 1 ) relaxation process of hydrogen nuclear magnetization was found in a series of hydrogenated amorphous carbon samples prepared under different self-bias conditions from benzene. The temperature dependence of these relaxation times reveals the different dynamic background of the two sub-systems. Low activation energies (depending on self-bias voltages) were measured for the longer relaxation time components; temperature independence was detected for the shorter relaxation time components.

The proton NMR line shift with respect to water, the bulk susceptibility and in a few cases the Korringa contribution to the spin lattice relaxation time were measured in Zr0.33Ni0.67 Hx amorphous alloys with hydrogen concentration 0.1 ⩽ x ⩽ 0.7and at 343 K. All the parameters, including the hydrogen content and the bulk susceptibility, were measured simultaneously in situ, and in the shift measurements a resolution of ±1 ppm was attained. The residual Knight shift depends on the hydrogen content and is positive relative to water. Preliminary low temperature spin lattice relaxation time measurements indicate that the positive shift is the consequence of the balance of s- and d-contributions.

Proton magnetic resonance spectra of Zr 0.5 Cu y Ni 0.5−y H 1 metallic glass samples with 0 ≤ y ≤ 0.3 were measured in the temperature range 77 K to 400 K and at 8, 28.5, 87.6 and 88.5 MHz frequencies. The data of the free-induction decay (FID) signal were compiled and Fourier transformed by a SMIS NMR spectrometer. The temperature dependence of the line shapes shows three distinctly different features: (i) in the temperature range 400 K to 270 K the spectrum is a motionally narrowed Lorentzian line; (ii) in the temperature range 270 K to 140 K the spectrum consists of a narrow Lorentzian component and a substantially wider Gaussian one; (iii) in the temperature range 140 K to 77 K, the spectrum is a “two-peaked” line. The distance between the two peaks (splitting) was found to be independent of the temperature and the frequency, that means that the low-temperature spectrum is probably the Pake doublet of hydrogen pairs. From the analysis of the splitting of the Pake doublet, a proton-proton distance of 0.167 nm was estimated. This distance corresponds to a transition metal mediated hydrogen pairing.

Accurate measurements of small 31P Knight shift effects in crystalline Ni3P and Cu3P alloys have been performed by using a magic-angle spinning (MAS) nuclear magnetic resonance (NMR) technique. Both the average Knight shift and the width of its distribution have been found to be different when comparing a normal (equilibrium) and a melt-quenched Ni3P alloy and this is attributed to possible differences in defect concentration and grain size. The 31P NMR line shift of Cu3P is much smaller (K=0.012%) than that of Ni3P (K=0.179%) but spin-lattice relaxation time measurements indicated a Korringa-type relaxation mechanism for both alloys, i.e. Cu3P has also a metallic character.

The proton rotating-frame spin lattice relaxation time T1r has been measured in (Ni0.5Zr0.5)0.95P0.05H0.54 and (Ni0.5Zr0.5)Po0.07H0.58 amorphous alloys in the temperature range 140–370 K. A single-exponential relaxation decay was obtained from 200 to 370 K only. The experimental data above 200 K were interpreted on the basis of a model involving diffusion of the hydrogen atoms. It is demonstrated that, by using a gaussian distribution of diffusion activation energies about a temperature independent mean energy E a = 0.32 eV atom−1 and a full width at half maximum ΔE = 0.07 eV, the temperature dependence of T1r can be well fitted in the 200–370 K range. These values are compared with relevant hydrogen diffusion data from the literature on other amorphous alloys

Cubane (C8H8) and fullerene (C60) are famous cage molecules with shapes of platonic or archimedean solids. Their remarkable chemical and solid-state properties have induced great scientific interest. Both materials form polymorphic crystals of molecules with variable orientational ordering. The idea of intercalating fullerene with cubane was raised several years ago but no attempts at preparation have been reported. Here we show that C60 and similarly C70 form high-symmetry molecular crystals with cubane owing to topological molecular recognition between the convex surface of fullerenes and the concave cubane. Static cubane occupies the octahedral voids of the face-centred-cubic structures and acts as a bearing between the rotating fullerene molecules. The smooth contact of the rotor and stator molecules decreases significantly the temperature of orientational ordering. These materials have great topochemical importance: at elevated temperatures they transform to high-stability covalent derivatives although preserving their crystalline appearance. The size-dependent molecular recognition promises selective formation of related structures with higher fullerenes and/or substituted cubanes.

For determination of the hydrogen content in metallic samples the gravimetric method is generally used, but the large change of the electrical resistivity observed on H-absorption can also be used. The latter method is very effective if the time dependence of the process is important. The resistivity change of the sample can easily be used for monitoring the H-absorption in a gas atmosphere and with some caution for the determination of the H content in galvanic doping as well. Results are presented for the Zr33Ni67 amorphous alloy with both methods of H charging.

The field-independent 31P NMR linewidth, δHo, is measured in nonmagnetic amorphous Ni-based alloys. In addition, the second moment contribution M originating from direct nuclear dipole–dipole interaction is calculated using Van Vleck's theory based on a computer generated DRPHS amorphous model cluster. The calculated second moment M and the experimental second moment M obtained from δHo by Gaussian line shape approximation (i.e., M = (δHo)2/4) agree fairly well for a (Ni0.27Cu0.73)82P18 metallic glass. In the case of amorphous NiP and NiPB alloys M exceeds M by a factor of two or three. This excess second moment seems to indicate the presence of some indirect indirect interactions between nuclear spins. [Russian Text Ignored].

Multiphase oxide superconductors of nominal compositions Tl 2 BaCa 2 Cu 3 O x have been synthesized and characterized by resistivity and magnetic susceptibility measurements. NMR spin echoes of both thallium isotopes ( 203 Tl and 205 Tl) have been detected and the line shifts, the spin-lattice and spin-spin relaxation times have been measured at room temperature for the more abundant 205 Tl nuclei. The temperature dependence of the spin-lattice relaxation rate is also reported. The results suggest that, similarly to the behavior of Y in YBa 2 Cu 3 O 7 oxides, Tl has a small electronic density of states at the Fermi level in the Tl-Ba-Ca-Cu oxide superconductors.

The electronic structure of amorphous ZrNiP and ZrNiPH alloys was studied by means of ultraviolet photoemission spectroscopy. It was established that new states were induced around 5.7 eV binding energy by hydrogen and, at the same time, the density of states (DOS) at the Fermi level decreased. The Ni peaks below the Fermi level are shifted to higher binding energies upon hydrogenation whereas the position of the Zr peak remains unchanged but its intensity is reduced due to the presence of hydrogen. The decrease of the DOS at the Fermi level indicates that H atoms interact with Zr atoms only. On the other hand, the clear shift in the Ni d-states shows that the Ni states are affected by hydrogen via changes in the ZrNi bonding.

A magic-angle spinning nuclear magnetic resonance (NMR) study of the Knight shift effects in rapidly quenched alloys is presented. The 31P NMR of the melt-quenched crystalline Ni3P alloy shows that the average Knight shift and the distribution of isotropic shifts are significantly different from the corresponding values for normal crystals. The results are explained as off-stoichiometry and grain size effects on the electronic structure respectively. The NMR of hydrogen in a ZrNiP-type melt-quenched amorphous alloy shows a dependence of the average Knight shift and isotropic Knight shift distribution on the hydrogen content. These results can be explained by assuming a dilatation of the metallic matrix and by specific hydrogen dynamics respectively.

Conductance noise measurements done on (melt-quenched) glassy metal point contacts are reported. The lower limit of the noise factors obtained was stronger by 3–5 orders of magnitude than that usual in ordinary metals. That result supports well the view about the role of defects in generating the 1/f noise, but there are some doubts, whether the relevant defects are necessarily mobile.

Room temperature measurements are presented of the 31P NMR Knight shift and the T1 and T2 relaxation times for several frequencies in Ni100−xPx (17.1 ≦ x ≦ 26.8) and Cu60Ni22P18 amorphous alloys. The experimental results are analysed in terms or the Korringa relation and of the possible electronic structure of these metallic glasses.

Conductance noise measurements done on point contacts of (melt-quenched) glassy metal ribbons are reported. The lower limit of the 1/f noise factor obtained was stronger by 3-5 orders of magnitude than that usual in ordinary metals. That result supports the "two potential well tunelling" model of 1/f noise in glassy metals. The conductance fluctuations measured in hydrogenized glassy metals proved to be also 1/f noise. Diffusion noise due to hydrogen has not been found.