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Diffusion of calcium in calcium tungstate single crystals
Vol. 5, No. 8 15.
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
v
DIFFUSION OF CALCIUM IN CALCIUM TUNGSTATE SINGLE CRYSTALS Y. P. Gupta and L. J. Weirick (School of Mineral and Metallurgical Engineering, University of Minnesota, Minneapolis, Minnesota)
ordre. Le modèle met en outre en evidence une transformation normalisatrice réduisant les isothermes d’aimantation de toute substance, ferro ou anttferromagnêtique, a. un réseau d’isothermes universelles.
The self-diffusion of Ca in single crystal
Landau’s ideas about phase transitions are found to be well illustrated, within the frame-
CaWO4 doped with Nd and Na has been measured in the temperature range 0. 53 T - 0.9 T1. From 0. 75 T~ - 0. 9 T~,D = (4. 0 ±0. 3) / 55 800 620 ~ 2 sec1 and x 10~ exp (~- ~ cm from 0.53 to 0.75 T 1, D = (1.9 ± 0.4) x 10—8 2 sec1 • 22 900 1 100 exp ‘ RT ‘ cm In the range 0. 75 TE - 0. 9 T 1, diffusion appears to be intrinsic lattice diffusion, via a vacancy mechanism. In CaWO4 the predominant intrinsic defect structure appears to be 2~and the Schottky defect The with energy vacancies on the Caof the 02 sites. of formation Schottky defect pairs is estimated to be 52 to 66 kcal/g. mole.
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work of molecular field theory, by an Ising antiferromagnet in a magnetic field. One comes upon the various types of transition considered by Landau: “quantitative” transition without a changetransitions, of symmetry, firstones andbeing second order phase the and latter both studied in detail, particularly in the vicinity of 0°Kand of the so-called “critical point” where a first order one.phase The transition model demonstrates a the second order changes into general transformation normalizing the magnetization isothermals of any substance, ferro or anttferromagnetic, to a net of universal mothermals. (Received 16 February 1967) (Revised 29 May 1967) 17.
In the temperature range 0.53 T~- 0.75
NUCLEAR MAGNETIC RESONANCE OF F~IN RARE EARTH TRIFLUORIDES
T 1, Ca diffusion in CaWO4 appears to be extrinsic. Diffusion profiles for samples annealed at lower temperatures lead to two values of D. (Received 15 May 1967) (Revised 29 June 1967) 16.
ANTIFERROMAGNETISME DANS UN CHAMP MAGNETIQUE I. TRAITEMENT DE CHAMP MOLECULAIRE R. Bidaux, P. Carrara et B. Vivet (Service de Physique du Solide et de Resonance Magnetique, centre d’Etudes Nucléaires de Saclay, BP No. 2, 91, Gif-sur-Yvette, France) -
Le modèle de champ moléculaire, appliqué a. un antiferromagnetique d’Ising place dans un champ magnetique, se révèle être une excellente ifiustration des idées de Landau sur les transitions de phase. On rencontre en effet les divers types de transition envisages par celui-ci: transition “quantitative” sans changement de symétrie et transition de phase du premier et du second ordre; ces dernières font l’objet d’une étude détaillée, en particulier au voisinage de 0°Ket du “point critique” de raccordement entre les lignes de transition du premier et du second
V. Saraswati and R. Vijayaraghavan (Tata Institute of Fundamental Research, Bombay, India) Nuclear magnetic resonances of F~in rare earth trifluorides have been measured. The width and shift at any temperature is proportional to the moment of the rare earth ion and follow the susceptibility measurements of Kern and Raccah. A finite and negative shift of -0.3 ± 0.1% has been observed in GdF3 which agrees with -0. 46%, expected from the spin polarization calculation of Freeman and Watson. Apart from the usual paramagnetic broadening, resonance widths exhibit diffusion narrowing for the cerium group rare earth fluorides. (Received 8 May 1967) (Revised 12 June 1967) 18.
HIGH ELECTRONIC SPECIFIC HEAT OF h. c. p. Fe-Ru ALLOYS H. Claus (Department of Metallurgy, Untversity of Illinois, Urbana, Illinois)
Low temperature specific heat measurements in the range of 1.4 to 4. 2°K were made with the three h. c. p. alloys: Fe~Ru,~, Fe~Ru~
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
v
DIFFUSION OF CALCIUM IN CALCIUM TUNGSTATE SINGLE CRYSTALS Y. P. Gupta and L. J. Weirick (School of Mineral and Metallurgical Engineering, University of Minnesota, Minneapolis, Minnesota)
ordre. Le modèle met en outre en evidence une transformation normalisatrice réduisant les isothermes d’aimantation de toute substance, ferro ou anttferromagnêtique, a. un réseau d’isothermes universelles.
The self-diffusion of Ca in single crystal
Landau’s ideas about phase transitions are found to be well illustrated, within the frame-
CaWO4 doped with Nd and Na has been measured in the temperature range 0. 53 T - 0.9 T1. From 0. 75 T~ - 0. 9 T~,D = (4. 0 ±0. 3) / 55 800 620 ~ 2 sec1 and x 10~ exp (~- ~ cm from 0.53 to 0.75 T 1, D = (1.9 ± 0.4) x 10—8 2 sec1 • 22 900 1 100 exp ‘ RT ‘ cm In the range 0. 75 TE - 0. 9 T 1, diffusion appears to be intrinsic lattice diffusion, via a vacancy mechanism. In CaWO4 the predominant intrinsic defect structure appears to be 2~and the Schottky defect The with energy vacancies on the Caof the 02 sites. of formation Schottky defect pairs is estimated to be 52 to 66 kcal/g. mole.
)
~•
)
work of molecular field theory, by an Ising antiferromagnet in a magnetic field. One comes upon the various types of transition considered by Landau: “quantitative” transition without a changetransitions, of symmetry, firstones andbeing second order phase the and latter both studied in detail, particularly in the vicinity of 0°Kand of the so-called “critical point” where a first order one.phase The transition model demonstrates a the second order changes into general transformation normalizing the magnetization isothermals of any substance, ferro or anttferromagnetic, to a net of universal mothermals. (Received 16 February 1967) (Revised 29 May 1967) 17.
In the temperature range 0.53 T~- 0.75
NUCLEAR MAGNETIC RESONANCE OF F~IN RARE EARTH TRIFLUORIDES
T 1, Ca diffusion in CaWO4 appears to be extrinsic. Diffusion profiles for samples annealed at lower temperatures lead to two values of D. (Received 15 May 1967) (Revised 29 June 1967) 16.
ANTIFERROMAGNETISME DANS UN CHAMP MAGNETIQUE I. TRAITEMENT DE CHAMP MOLECULAIRE R. Bidaux, P. Carrara et B. Vivet (Service de Physique du Solide et de Resonance Magnetique, centre d’Etudes Nucléaires de Saclay, BP No. 2, 91, Gif-sur-Yvette, France) -
Le modèle de champ moléculaire, appliqué a. un antiferromagnetique d’Ising place dans un champ magnetique, se révèle être une excellente ifiustration des idées de Landau sur les transitions de phase. On rencontre en effet les divers types de transition envisages par celui-ci: transition “quantitative” sans changement de symétrie et transition de phase du premier et du second ordre; ces dernières font l’objet d’une étude détaillée, en particulier au voisinage de 0°Ket du “point critique” de raccordement entre les lignes de transition du premier et du second
V. Saraswati and R. Vijayaraghavan (Tata Institute of Fundamental Research, Bombay, India) Nuclear magnetic resonances of F~in rare earth trifluorides have been measured. The width and shift at any temperature is proportional to the moment of the rare earth ion and follow the susceptibility measurements of Kern and Raccah. A finite and negative shift of -0.3 ± 0.1% has been observed in GdF3 which agrees with -0. 46%, expected from the spin polarization calculation of Freeman and Watson. Apart from the usual paramagnetic broadening, resonance widths exhibit diffusion narrowing for the cerium group rare earth fluorides. (Received 8 May 1967) (Revised 12 June 1967) 18.
HIGH ELECTRONIC SPECIFIC HEAT OF h. c. p. Fe-Ru ALLOYS H. Claus (Department of Metallurgy, Untversity of Illinois, Urbana, Illinois)
Low temperature specific heat measurements in the range of 1.4 to 4. 2°K were made with the three h. c. p. alloys: Fe~Ru,~, Fe~Ru~