The time differential perturbed γ-γ angular correlation technique (TDPAC) is applied to the amorphous metallic systems Ga, Bi, In50Au50 and In80Ag20. The electric field gradient tensor probed by 111Cd nuclei shows a broad probability distribution with a relative width of 0.4 – 0.5 for all systems, as suggested by a continuous random structural model.

The perturbed angular correlation technique has been applied to study the local environment of tantalum in nickel after ion implantation of hafnium and after laser-pulse melting. The magnetic hyperfine interaction at the daughter nucleus tantalum in nickel is used to determine the uniqueness of the tantalum lattice site. Several hafnium concentrations were employed and auxiliary measurements using ion-beam channeling, Rutherford backscattering and Auger electron spectroscopy were performed.

The electric field gradient (efg) present in noncubic solids causes an energy–splitting of the nuclear levels via the quadrupole hyperfine interaction. During the last few years the perturbed angular correlation method has proved a unique experimental tool for investigating this interaction especially in metals. The basic principles of the method are discussed. Recent experimental results are given for pure metals and highly diluted systems as well as for alloys and intermetallics. The last section deals with theoretical aspects of the temperature dependence of the efg in pure metals.

A high purity Cu target foil doped with 57Co and cooled to 80 K has been deuteron irradiated (E = 2 MeV to .5 MeV) using a Van de Graaff accelerator. In-situ Mössbauer spectra of the target were taken as a function of deuterium dose and post irradiation annealing. Two new 57Co sites are observed in addition to the original substitutional site. The new site ‘1’, populated at low temperature following the irradiations is identified with a 57Co impurity atom having Cu-interstitials trapped in its immediate vicinity. The new site ‘2’, populated on annealing the target above 360 K is believed to represent a 57Co impurity having deuterium localized in its vicinity.

Muon diffusion can be studied in metals without nuclear moments by the addition of paramagnetic impurities. We describe the theory and report measurements of muon depolarization in gold and silver doped with gadolinium and erbium. As well as diffusion rates, strength of the magnetic interaction and spin lattice relaxation rate of the paramagnetic ion are inferred from the data.

Internal oxidation of indium in a silver matrix is studied by time-differential perturbed angular correlations. The oxidizer treatments were performed in air at 1 atm. Our results are consistent with the formation of different In-O complexes.

We report the first use of nuclear magnetic resonance to investigate dislocation motion in metals. The spin-lattice relaxation rate in the rotating frame T 1ρ−1, of 27Al in polycrystalline, ultrapure Aluminium foils has been measured as a function of plastic-deformation rate έ for two different temperatures (77K and 300K). For έ = 0, the relaxation rate is determined by conduction electrons. For a finite deformation rate έ, an additional contribution to the relaxation rate arising from fluctuations in the nuclear quadrupole interaction due to dislocation motion is observed. From the motion-induced part of the relaxation rate the mean jump distance of a mobile dislocation is calculated which is determined by the density of lattice defects acting as obstacles for moving dislocations.

Uranium stannide, the most stable intermetallic compound in the Uranium/Sn system, has the Cu3Au(LI2 ) structure, and is paramagnetic to liquid He temperature. The magnetic susceptibility data are consistent with 5f band states rather than a localized electronic structure. Samples of this compound have been prepared both with depleted and 235U enriched, as well as 119Sn enriched starting material. Detailed 119mSn Mössbauer effect studies have been carried out over the temperature range 78≤T≤300 K on 60Co gamma ray irradiated, thermal neutron irradiated (depleted), and thermal neutron irradiated (enriched) samples, using the V 10 position of the Brookhaven HFR facility for the neutron irradiations (thermal/fast >3.6×102). The Mössbauer hyperfine parameters are: IS(78) = 2.45 mm/sec, Q.S.(78) 1.38 mm/sec for the unirradiated samples, consistent with the metallic nature of Sn in the USn3 structure. No anomalous charge states have been identified in the Mössbauer spectra of the gamma or neutron irradiated samples. The free-atom lattice temperature is ∼250 K for the unirradiated sample, and shows only minor changes with 60Co–γ radiation to a total dose of 1000 Megarad. Thermal neutron radiation (nvt ∼5×1016 ) of the depleted sample results in a lowering of the lattice temperature to ∼240 K. Two hours heating at 800°C are sufficient to anneal the radiation damage as judged by lattice dynamical data. A sample enriched to 99.94% 235U and irradiated to a fluence of ∼5×1015 slow neutrons/cm2 showed an increase in the freeatom lattice temperature to ∼275 K. A two hour anneal at 800°C restored this parameter to its original value. Resistivity data for these samples and their relationship to spin fluctuation temperatures will also be discussed.

The perturbed angular correlation technique (TDPAC) was applied to determine the orientation of the electric field gradient tensor induced by lattice defects at the probe 1l1In. The experimental results obtained for self-interstitials, vacancies and defect clusters in Cu, Ag and Au are shown and their microscopic interpretation is discussed.

With the perturbed angular correlation and distribution methods we studied the trapping and annealing of lattice defects in the hcp metals Cd and Zn. The defects were produced (i) by proton irradiation, (ii) by quenching, and (iii) by heavy ions recoiling after a nuclear reaction As probe ions we used 111Cd (i,ii) and 67Ge,69 Ge,71 Ge,113 Sn, and116 Sn (iii). The In-impurities in Zn and Cd are trapping centers for vacancies. At low temperatures (100 to 200 K) simple defect configurations are observed. In the in–beam experiments a sharp annealing step due to detrapping of vacancy type defects is found.

NMR results in RE-Fe2 internmtallic compounds at low temperatures are reported. Using a spin-echo spectrometer in the U.H.F. range, hyperfine field parameters have been measured on 167Er, 163Dy, 169 Tn and 159Tb at 1.4K. These cctnpounds have high Curie temperatures and the magnetic moment of the rare-earth, gJμB<Jz> is nearly saturated. The value of the iron moment is also known from Mossbauer measurements and accurate data for the hyperfine field at the rare-earth site obtained from NM enables us to extract the internal field due to conduction electrons.

A summary of the magnetic properties of three Laves Phases compounds RFe2 (R = Pr, Nd, Yb) synthesized under high pressure is presented. Most of the results have been obtained by Mössbauer spectroscopy. Through the 57Fe resonance, the easy directions of magnetization between 4 and 300 K have been determined; the hyperfine field at Fe contains a large anisotropic contribution, only partly due to dipolar effects. From the Yb170 Mössbauer resonance measurements in YbFe2, the exchange field of the iron and the crystalline field, acting on Yb3+, have been derived.

In the system (FeXNi1−x)75P16B6Al3 an unusual magnetic behaviour is found in the composition range 0.2<x<0.3. The drastic changes seen at low temperature in the thermomagnetic measurements is found not to affect the Mössbauer spectra. From the width of the magnetic hyperfine field distribution as function of temperature there seems to be a distribution in Curie temperatures. Due to the absence of spin texture it was not possible to make a distinction between the two proposed low temperature phases although the general results favour the spin glass alternative.

The systematic variations of experimentally determined exchange and hyperfine (h.f.) interactions between Eu2+ ions are compared firstly within the EuX (X=0,S,Se,Te) series of compounds and secondly in the magnetic dilution system EuxSr1−xS. Reasonably relations can be established between the individual nearest and next nearest neighbour exchange interactions (J1,J2 ) and the transferred h.f. interactions (ΔB1 , ΔB2 ), respectively, by considering their variations with the Eu–Eu distances (R1,R2). Using these results, the measured mean hyperfine field, BI(x), and the ferromagnetic saturation h.f. field, B↑↑ (x), of the EuxSr1−xS system can be related reasonably well to the ferro- and paramagnetic phase boundaries, Tc(x) and θ (x), respectively.

Lanthanide orthophosphates formed from elements in the first half of the 4f transition series are analogs of the monoclinic mineral monazite. The known geologic properties of this mineral make the general class of lanthanide orthophosphate compounds attractive substances for long-term containment and disposal of α-active actinide nuclear wastes. EPR spectroscopy has been used to investigate the structural properties and solid state chemical properties of impurities in these materials and to compare the characteristics of single crystals and polycrystalline bodies.

Dislocation motion in alkali halide single crystals is strongly impeded by the presence of impurities, apart from obstacles built by the forest dislocations. The mean free path L of stepwise moving dislocations is measured by determination of the spin-lattice relaxation rate 1/T1ρ as a function of the strain rate έ, varying the content of impurities and the temperature. The latter influences the distribution of the point defects and the activation rate of dislocations before obstacles, while the former merely shorten L, thereby raising 1/T1ρ.

Longitudinal muonium spin relaxation/modulation in zero magnetic field (zf-MSR) has been used to study muonium (μ+e-) atoms in single-crystal α-quartz between 5 K and room temperature. At 6 K, three frequencies are observed, corresponding to a triaxial hyperfine matrix whose principal values are close to those observed for hydrogen atoms frozen into known sites. For intermediate temperatures the Mu atoms “hop” between sites, causing a relaxation whose rate first increases with the hop rate and then decreases due to motional narrowing. Finally, at room temperature, a single-frequency oscillation is observed, corresponding to a uniaxial motionally-averaged hyperfine interaction.

57 Fe and 125 Te Mössbauer data on the spinels LiFeNi3TeO8 and LiFeCo3TeO8 are presented. Structural information relating to site occupations by Fe, valency of Fe and Te and magnetic hyperfine fields are obtained from this study.

The proton free induction decay f(t) of ammonium selenate is measured from temperatures of no apparent effects of lattice motion (−185°C) upon f(t), to substantial motional effects (−145°C) upon f(t). Our measured results are consistent with a classical hindered rotational motion of the ammonium group. The deviation of f(t) from the rigid-lattice fid fo(t) can be expanded in a Taylor series as

From the Δ1f(t) data, a3 and a4 are derived, and they are well fitted by the simple relations

where ν is the jump frequency of the rotational motion, T1r is the rotating-frame spin-lattice relaxation time, and ω1 the strength of the rotating magnetic field in frequency units. α, C3 and C4 are calculable constants of order unity.

FeOCl is a layered compound belonging to the orthorhombic space group Pmnm (D2h13), with two formula units per unit cell. Adjacent layers in the (010) crystallographic plane, in which chlorine atoms face each other, are held together by van der Waals forces which are readily disrupted by the insertion of appropriate Lewis base molecules. This intercalation of “guest” species causes an expansion in the b-direction, leaving the remainder of the unit cell dimensions unchanged. Among base molecules which are readily intercalated are NH3, pyridine and a wide variety of substituted pyridines, nitrogen containing heterocyclic molecules, phosphines and phosphites. The limiting stoichiometry ranges from 1:3 (“guest” to Fe atom ratio) for small intercalants to 1:6 for large “guest” molecules. Using both powder X-ray diffraction and temperature dependent 57 Fe Mössbauer effect spectroscopy, the lattice dynamics, hyperfine interactions, magnetic ordering temperature and magnetic hyperfine field (at 4.2 K) have been studied for the neat matrix and a number of base intercalates. The magnetic hyperfine field at the iron atom at 4.2 K is 441╪3 KOe, independent of the magnitude of the b-axis expansion. Vzz is negative for neat FeOCl and intercalates in which the “guest” to host ratio is ≤ 1:3, and positive when this ratio is ≥ 1:4.