J. H. Wernick

Superconductivity with onset above 23° K in NbGe sputtered films

Abstract Sputtered films of nominal composition Nb 3 Ge deposited onto hot substrates, of the type recently found by Gavaler to have superconductivity onsets at 22.3° K, have now been obtained with a maximum onset temperature of 23.2 ± 0.2° K and a transition width of ∼ 1.2° K. The sputtering conditions necessary to achieve these results are discussed and suggest that the high T c phase may be detrimentally affected by the presence of high energy particles present under normal sputtering conditions.

Linear and nonlinear optical properties of ternary A II B IV C 2 V chalcopyrite semiconductors

The refractive indices of ZnSiAs 2 , CdGeP 2 , and CdGeAs 2 have been determined over a wide range of wavelengths and the optical nonlinear coefficient for second-harmonic generation from the 10.6-μ CO 2 laser have been measured. The absorption coefficient versus wavelength is given for the above materials as well as for ZnGeP 2 , a previously discussed material. Three-frequency phase-matched mixing is described for each material.

Magnetic Moments of Intermetallic Compounds of Transition and Rare‐Earth Elements

The effect of adding the rare‐earth elements to cobalt, iron, and nickel has been investigated. Antiferromagnetic coupling was found to exist in the cobalt and iron rare‐earth compounds. The moment per formula unit of the compound Co5Y is increased when Sm, Pr, and Nd are substituted for yttrium and decreased when Tm, Gd, Tb, Er, Dy, and Ho are substituted. This is explained on the basis that although the spin moments of cobalt and rare earths are coupled antiferromagnetically in these compounds, the orbital moments add to the cobalt moment in the compounds containing Sm, Pr, and Nd, but they subtract from the cobalt moment in the compounds containing Tm, Tb, Er, Dy, and Ho. For the iron compounds investigated, the moment of the compound Fe4Y was found only to decrease when Tm, Er, Ho, and Dy were substituted for yttrium. The nickel compounds behaved entirely differently from the cobalt and iron compounds since very little or no antiferromagnetic coupling was observed in these compounds.

NEW PERMANENT MAGNET MATERIALS.

New permanent magnet materials containing rare‐earth elements (RE) have been discovered. For the most part, these alloys are based on the hexagonal intermetallic compounds, Co5RE. Replacement of cobalt with copper in some of these rare‐earth compounds results in solid materials with substantial permanent magnet properties. Coercive forces as high as 28,700 Oe have been obtained in heat‐treated samples of alloys in the Co5Sm–Cu5Sm system.

XPS core line asymmetries in metals

Abstract A systematic study of the shape of core lines obtained by X-ray photo-emission spectroscopy (XPS) is reported. The analysis in terms of the theory of Nozieres and De Dominicis shows that for sp metals the results can be interpreted in terms of a phase shift analysis. For transition metals the ssd interaction makes an important contribution to the observed asymmetries.

Magnetic behavior of the monosilicides of the 3d-transition elements

The magnetic behavior of the monosilicides of Cr, Mn, Fe, and Co, as well as of solid solutions among them, is presented. Special emphasis is given to the development of localized moments in CoSi-based solid solutions. Long range magnetic order is found in Col−xFexSi alloys near the middle of the composition range.

Metamagnetism of Some Rare‐Earth Copper Compounds with CeCu2 Structure

Magnetic moments of the series of rare‐earth copper (RCu2) intermetallic compounds have been measured at temperatures from 1.4° to 300°K. These compounds have an orthorhombic crystal structure and are isostructural with CeCu2. The susceptibility at high temperatures of most of the compounds followed the Curie—Weiss law giving effective moments close to those of the trivalent rare‐earth ions. Eu and Yb appeared to be divalent. At low fields antiferromagnetic behavior was indicated in some of these compounds by peaks in the curves of moment vs temperature, and by a lack of remanence. Metamagnetic behavior was observed when measurements were made at 4.2°K and with fields up to 80 000 Oe. For example, the moment of TbCu2 increased abruptly at a critical field, and at 80 000 Oe, although not yet saturated, had a moment of 6.2 Bohr magnetons. The moments of EuCu2 and GdCu2 increased gradually, and at 80 000 Oe reached moments of 5.7 and 6.0 Bohr magnetons, respectively. These results indicate a relatively weak ...

Degradation of LaNi5 by temperature-induced cycling

Abstract We studied the hydrogen absorption-desorption properties of LaNi 5 and (La 0.9 Eu 0.1 )Ni 4.6 Mn 0.4 for 1500 thermally induced cycles at approximately 8 – 20 atm and found that the amount of reversibly absorbed hydrogen decreased markedly. In addition to the gas absorption measurements, X-ray measurements and Mossbauer spectroscopy studies of 151 Eu in the intermetallic were performed. Combining the results of these measurements we established that the degradation occurs via the formation of a stable hydride phase rather than via oxidation by water or oxygen impurities. The degradation that we observe is thus an intrinsic process. We believe this to be the first report of intrinsic degradation of the gas-absorbing properties in LaNi 5 . The results are discussed in the light of recent magnetization measurements on pressure-cycled LaNi 5 .

The high field-high pressure magnetic properties of MnSi

Abstract Experiments at high pressures and magnetic fields indicate that although MnSi is an unsaturated ferromagnet it cannot be characterized as a simple weak itinerant one.

The crystal structure and magnetic properties of the rare-earth nickel (RNi) compounds

Abstract The crystal structure of GdNi has been accurately determined and the lattice constants of eleven isomorphous rare-earth nickel (RNi) compounds, with the CrB type structure, measured. The magnetization of these compounds has been measured as a function of temperature in a field of 14.24 kOe. Saturation magnetization measurements were made at 4·2°K in fields up to 80 k0e. The effective paramagnetic moments agree excellently with the theoretical moments of free R 3+ ions. The Curie temperatures of the RNi compounds have been determined and compared with those of the RNi 2 and RNi 5 compounds. The spin moments appear ferromagnetically aligned parallel with the crystal b -axis, normal to the puckered sheets of R and Ni atoms comprising the crystal. A single crystal of SmNi exhibits a coercive force of 35 kOe at 1·4°K. The most important interatomic distances are Ni-Ni at 2·614, Gd-Ni at 2·903, 2·917 and 2·954 A, and Gd-Gd at 3·588 and 3·631 A. The smoothed volume change between LaNi and LuNi is −17 per cent.