Temperature and magnetic field dependence of the elastic properties of the HoxTb1−xCo2 laves phase compounds

Vol. 33, No.4 ABSTRACTS OF ARTICLES TO BE PUBLISHED IN THE J. PHYS. CHEM. SOLIDS ix 2~ host from intensities of lines at liquid helium temperaElectron paramagnetic resonance spectra of Cu doped in single crystal of anhydrous sodium oxalate ture; for the Ce 2 (SO4 )~8H~Ohost the lines broaden grown by slow evaporation from saturated aqueous considerably below 60 K, not permitting the determinsolutions have been investigated. EPR measurements ation of absolute signs of spin Hamiltonian parameters. gave the following values for the spin Hamiltonian The data are analysed using a rigorous least-squares parameters: ~ = ~ = 2.0741, g,~= 2.3253, procedure, fitting simultaneously all lines obtained for A~ = ~ = 14.9 G and ~ = 147.7G. The several orientations of the external magnetic field. The principal axes of the hyperfme coupling and g tensors zero-field splittings have been computed for both 3~inthe are spatially optical we absorbtion hosts.hosts The characteristics of EPR spectra of Gdin other energy valuescoincident. given for aUsing similarthe complex have these are compared with those obtained estimated the values of the bonding parameters and rare-earth trisuiphate octahydrate hosts. orbital-reduction factors for the system under Received 20 June 1979 investigation. Revised 28 September 1979 Received 22 June 1979 Revised 14 September 1979 20. TEMPERATURE AND MAGNETIC FIELD DEPENDENCE OF THE ELASTIC 18. APW-Xa COMPTON PROFILES IN PROPERTIES OF THE Ho~Tb 1..~Co2LAVES CRYSTALLINE RARE GASES PHASE COMPOUNDS J.P. Worth, Corinne Lee Merry and S.B. H. Klimker, M.P. Dariel and M. Rosen, Nuclear Trickey, Quantum Theory Project, Department Research Center-Negev, Beer Sheva, Israel; and of Physics, University of Florida, Gainesville, Materials Engineering Department, Ben-Gurion FL 32611, U.S.A. University of the Negev, Beer Sheva, Israel. —

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Augmented plane wave, local exchange (APW-Xi) one-electron wave functions have been used to calculate Compton profiles for crystalline Ne at three different lattice constants for two values of the local exchange parameter. Some results for Ar, Kr, and Xe are also presented. The impulse approximation is used. The crystalline calculations are little different from the isolated atom results. A variety of difficulties, primarily due to the energy-dependent nature of the APW basis, are explored. A translational symmetry restriction that is particularly severe for APW calculations of Compton profiles is studied. In all, it is concluded that the APW scheme is ifi-suited to the computation of the sort of non-energy quantity represented by a Compton profile. Received 20 August 1979 3~-DOPED 19. EPR STUDIES OF Gd Ce 2(S04)3. 8H2O and La2(S04)3 9H~O SINGLE CRYSTALS Sushil K. Misra and Pawel Mikolajczak, Department of Physics, Concordia UniversitySir George Williams Campus Montreal Canada H3G lM8 3~-doped Ce • EPR spectra of Gd 2 (SO4 )~8H20 and La2 (SO4 )~9H~Osingle crystals have been measured with an X-band spectrometer at room and low temperatures. The absolute signs of spin Hamiltonian parameters have been determined for the La2 (SO4)39H2O

Ultrasonic sound velocity measurements have been carried out in order to determine the adiabatic compressibility and elastic moduli of the pseudo-binary Ho~Th1_~Co2Laves phase compounds. The anomalies, associated with the Curie temperatures and the presence of various spin reorientations, allowed the determination of the spin orientation diagram with that previously established of the Ho~Tb~ -x Fe2 system strongly supports the single rare earth ion model for the magnetic anisotropy behavior of the compounds studied. Measurements carried out in an external magnetic field revealed the presence of significant L~,Eeffect. Received 12 June 1979 Revised 28 September 1979 21.

THIRD-ORDER ELASTIC CONSTANTS FOR 2:2 CHALCIDE CRYSTALSSTRUCTURE POSSESSING THE SODIUM CHLORIDE K.P. Thakur, School of Molecular Sciences, University of Warwick, Coventry CV4 7AL, England.

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Third-order elastic constants of 45 chalcide crystals •

hawng the sodium chloride structure are reported using Born—Mayer potential model. We have considered repulsive interaction up to second nearest neighbours. The temperature coefficients of the third-order elastic constants have also been computed for these crystals. As is the case for NaCl-type alkali halides we find that C~1 C1~2,C1~are negative and C1~are positive for ,