- Email: [email protected]
14. Contactless resistivity measurements on carbon fibers using a microwave perturbation technique
126
Abstracts
linearly with temperature. The samples heat-treated to 2500-3000°C show negative TEP with the characteristic phonon drag dip at around 35K. 11. Structure-and electrical properties of heat treated
coals J. Gonzalez-Hernandez,? Isaac Hernindez-Calderon, Carlos A. Luengo and Raphael Tsut (Institute de Fisica “Gleb Wataghin”, Universidade Estadual de Campinas, 13.100~Campinas, SP.-Brash). Applying the theories for
resistivity of the amorphous and granular materials, the temperature dependence of the electrical resistivity of coals, heat treated at different temperatures, has been successfully explained in terms of structural parameters obtained by X-ray measurements. tPresent address: Energy ConversionDevices, Inc., Troy, MI 48084.
12. The Hall effect, magnetoresistanceand electrical conductivity of glassy carbon Dennis F. Baker and Robert H. Bragg (Materials and
Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan). The transverse mag-
netoresistance of graphite is known to have a linear field dependence up to ca. 13T and tend to saturate at higher fields. The saturation value of Adpo is higher for purer samples. In single crystal graphite samples, whose resistance ratio &3OOK)/po(4K) is 20 or larger, a sudden increase of magnetoresistance was found in experiments using a 29T pulsed magnet. The critical field is 28T at 2SK and decreases to 24T with lowering temperature to 1.5K. An explication of this phenomenon in terms of an electronic phase transition induced by intense magnetic field is now being developed by Fukuyama.
16. Magnetorestriction in graphite J. Heremans, J-P. Michenaud, C. Haumont (Laboratoire de Physico-Chimie et de Physique de 1’Etat Solide Universite Catholique de Louvain, B- 1348 Louvainla-Neuue, Belgium) and M. Shayegan and G. Dresselhaus (Massachusetts Institute of Technology, Cambridge, MA 02139). The longitudinal magnetostriction of HOPG
Molecular Research Division, Lawrence Berkeley Laboratory and Department of Materials Science and Mineral Engineering, University of California, Berkeley, CA 94720). The Hall coefficient RH of glassy carbon is small, IRH( < 0.12 cm3/coul) and nearly insensitive to temperature T (2.5-1OOK)and magnetic field H (0-5T). The magnetoresistance is negative, proportional to Hz/T
graphite has been measured along the c-axis up to 15 Tesla. As magnetostriction is described by a coupling between elastic and magnetic energy the obtained results allow computing one deformation potential from the known band structure at high fields.
for low values, but less than the quantity so predicted for high values of Hz/T The conductivity can be formulated u = A exp - (XT-‘/~t B exp - fiT-“4. The Hall mobility is temperature insensitive and ~20 cm* V-’ see-‘.
17. Deformation potential for graphite M. S. Dresselhaus, Jos Heremans and G. Dresselhaus
13. Theory of the diamagnetism and g-shift of carbon fibers J. W. McClure, S. D. Elegba and B. Hickman (Department of Physics and Institute of Theoretical Science, University of Oregon, Eugene, OR 97403). The
magnetic susceptibility of folded graphite ribbons has been accurately obtained using calculated wavenumberdependent susceptibilities of finite-width ribbons. Fitting the experimental data provided values for the ribbon width and tightness of folding. Calculations of the ESR g-shift give a reasonable magnitude but the wrong sign. 14. Contactless resistivity measurementson carbon fibers using a microwaveperturbationtechnique I. L. Spain, A. Azzeer, C. E. Patton and L. Silber (Department of Physics, Colorado State University, Fort Collins, CO 80523) and H. A. Goldberg and I. Kalnin (Celanese Research Company, Summit, NJO7901). A
contactless technique for measuring the resistance per unit length of thin wires and fibers has been developed using microwave radiation of -9GHz. A carbon fiber, Celion@GY-70 gives unexpectedly high absorption. Possible reasons for this anomaly will be discussed.
(Massachusetts Institute of Technology, Center for Material Science and Engineering 13-2090, Cambridge, MA 02139). The form of the electronic g-band Hamil-
tonian in the presence of strain is derived. The expansion is carried out to first power in the strain, eir, and first power in the in-plane wave vector K. Evaluation of some of the deformation potential constants is made using magnetostriction measurements and measurements of the Fermi surface and magnetoreflection spectra under hydrostatic pressure.
18. Acoustomagnetoelectric effect in graphite Yoshiko F. Ohashi and Ko Sugihara (Keio Uniuersity, Faculty of Engineering, 3-14-l Hiyoshi, Kohoku-Ku, Yokohama 223, Jupan). Acoustomagnetoelectric effect
was investigated in graphite on applying longitudinal acoustic wave of 15.5MHz at liquid helium temperature in magnetic fields up to 50 kG. By making use of the theories of Cohen, Harrison and Harrison and Harrison, the observed results were analysed, which were different from those of bismuth by Yamada.
19. Raman scatteringfrom HOPC implanted with various iOIlS
B. S. Elman, G. Dresselhaus and M. Shayegan (M.Z.T, 15. Anomalous magnetoresistance of single crystal graphite S. Tanuma, A. Furukawa and Y. Iye (The Institute for
Center for Material Science and Engineering 13-3017, Cambridge, MA 02139). First and second order Raman
spectra
and electrical
properties
of
ion-implanted
Abstracts
linearly with temperature. The samples heat-treated to 2500-3000°C show negative TEP with the characteristic phonon drag dip at around 35K. 11. Structure-and electrical properties of heat treated
coals J. Gonzalez-Hernandez,? Isaac Hernindez-Calderon, Carlos A. Luengo and Raphael Tsut (Institute de Fisica “Gleb Wataghin”, Universidade Estadual de Campinas, 13.100~Campinas, SP.-Brash). Applying the theories for
resistivity of the amorphous and granular materials, the temperature dependence of the electrical resistivity of coals, heat treated at different temperatures, has been successfully explained in terms of structural parameters obtained by X-ray measurements. tPresent address: Energy ConversionDevices, Inc., Troy, MI 48084.
12. The Hall effect, magnetoresistanceand electrical conductivity of glassy carbon Dennis F. Baker and Robert H. Bragg (Materials and
Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan). The transverse mag-
netoresistance of graphite is known to have a linear field dependence up to ca. 13T and tend to saturate at higher fields. The saturation value of Adpo is higher for purer samples. In single crystal graphite samples, whose resistance ratio &3OOK)/po(4K) is 20 or larger, a sudden increase of magnetoresistance was found in experiments using a 29T pulsed magnet. The critical field is 28T at 2SK and decreases to 24T with lowering temperature to 1.5K. An explication of this phenomenon in terms of an electronic phase transition induced by intense magnetic field is now being developed by Fukuyama.
16. Magnetorestriction in graphite J. Heremans, J-P. Michenaud, C. Haumont (Laboratoire de Physico-Chimie et de Physique de 1’Etat Solide Universite Catholique de Louvain, B- 1348 Louvainla-Neuue, Belgium) and M. Shayegan and G. Dresselhaus (Massachusetts Institute of Technology, Cambridge, MA 02139). The longitudinal magnetostriction of HOPG
Molecular Research Division, Lawrence Berkeley Laboratory and Department of Materials Science and Mineral Engineering, University of California, Berkeley, CA 94720). The Hall coefficient RH of glassy carbon is small, IRH( < 0.12 cm3/coul) and nearly insensitive to temperature T (2.5-1OOK)and magnetic field H (0-5T). The magnetoresistance is negative, proportional to Hz/T
graphite has been measured along the c-axis up to 15 Tesla. As magnetostriction is described by a coupling between elastic and magnetic energy the obtained results allow computing one deformation potential from the known band structure at high fields.
for low values, but less than the quantity so predicted for high values of Hz/T The conductivity can be formulated u = A exp - (XT-‘/~t B exp - fiT-“4. The Hall mobility is temperature insensitive and ~20 cm* V-’ see-‘.
17. Deformation potential for graphite M. S. Dresselhaus, Jos Heremans and G. Dresselhaus
13. Theory of the diamagnetism and g-shift of carbon fibers J. W. McClure, S. D. Elegba and B. Hickman (Department of Physics and Institute of Theoretical Science, University of Oregon, Eugene, OR 97403). The
magnetic susceptibility of folded graphite ribbons has been accurately obtained using calculated wavenumberdependent susceptibilities of finite-width ribbons. Fitting the experimental data provided values for the ribbon width and tightness of folding. Calculations of the ESR g-shift give a reasonable magnitude but the wrong sign. 14. Contactless resistivity measurementson carbon fibers using a microwaveperturbationtechnique I. L. Spain, A. Azzeer, C. E. Patton and L. Silber (Department of Physics, Colorado State University, Fort Collins, CO 80523) and H. A. Goldberg and I. Kalnin (Celanese Research Company, Summit, NJO7901). A
contactless technique for measuring the resistance per unit length of thin wires and fibers has been developed using microwave radiation of -9GHz. A carbon fiber, Celion@GY-70 gives unexpectedly high absorption. Possible reasons for this anomaly will be discussed.
(Massachusetts Institute of Technology, Center for Material Science and Engineering 13-2090, Cambridge, MA 02139). The form of the electronic g-band Hamil-
tonian in the presence of strain is derived. The expansion is carried out to first power in the strain, eir, and first power in the in-plane wave vector K. Evaluation of some of the deformation potential constants is made using magnetostriction measurements and measurements of the Fermi surface and magnetoreflection spectra under hydrostatic pressure.
18. Acoustomagnetoelectric effect in graphite Yoshiko F. Ohashi and Ko Sugihara (Keio Uniuersity, Faculty of Engineering, 3-14-l Hiyoshi, Kohoku-Ku, Yokohama 223, Jupan). Acoustomagnetoelectric effect
was investigated in graphite on applying longitudinal acoustic wave of 15.5MHz at liquid helium temperature in magnetic fields up to 50 kG. By making use of the theories of Cohen, Harrison and Harrison and Harrison, the observed results were analysed, which were different from those of bismuth by Yamada.
19. Raman scatteringfrom HOPC implanted with various iOIlS
B. S. Elman, G. Dresselhaus and M. Shayegan (M.Z.T, 15. Anomalous magnetoresistance of single crystal graphite S. Tanuma, A. Furukawa and Y. Iye (The Institute for
Center for Material Science and Engineering 13-3017, Cambridge, MA 02139). First and second order Raman
spectra
and electrical
properties
of
ion-implanted