Electron spin resonance study of hot-pressed boron carbide

Journal Article · Tue Apr 15 04:00:00 EST 1986 · AIP Conf. Proc.; (United States)

DOI:https://doi.org/10.1063/1.35605· OSTI ID:5633803

Venturini, E L; Azevedo, L J; Emin, D; Wood, C

Electron spin resonance (ESR) spectra are reported for four hot-pressed boron-rich boron carbide samples B/sub 1-x/C/sub x/ in the composition range 0.1< or =x< or =0.2. At 2 K the spectra for all four compositions are characterized by a single Lorentzian absorption with a relatively narrow linewidth and free-electron g-value. The B/sub 4/C ESR linewidth remains narrow between 2 and 295 K, while the linewidth of the other three samples containing less carbon increases by a factor of 20 over this temperature range. Above 20 K the ESR signal in the latter three samples has a lineshape that cannot be described by a single Lorentzian, but can be explained as the sum of two Lorentzians with different linewidths, suggesting the presence of two distinct paramagnetic centers. The integrated intensities of the ESR signals in all samples follow a Curie law below 100 K, and the Currie constant corresponds to spin concentrations of 2 to 3 x 10/sup 19/ per gram. While these values are in agreement with static magnetic susceptibility data for samples cut from the same hot-pressed element, they are approximately two orders of magnitude less than the carrier densities estimated from transport measurements. This suggests that the carriers are spinless bipolarons.

• Research Organization: Sandia National Laboratories, Albuquerque, New Mexico 87185
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5633803
• Report Number(s): CONF-850786-
• Journal Information: AIP Conf. Proc.; (United States), Journal Name: AIP Conf. Proc.; (United States) Vol. 140:1; ISSN APCPC
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
&amp; Refractories-- Physical Properties
BORON CARBIDES
BORON COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CAVITY RESONATORS
CHARGE TRANSPORT
CURIE-WEISS LAW
DATA
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ELECTRONIC EQUIPMENT
EQUIPMENT
EXPERIMENTAL DATA
FABRICATION
FREQUENCY RANGE
GHZ RANGE
HOT PRESSING
INFORMATION
LANDE FACTOR
LINE WIDTHS
LOW TEMPERATURE
MAGNETIC RESONANCE
MATERIALS WORKING
MEDIUM TEMPERATURE
MICROWAVE RADIATION
NUMERICAL DATA
POLARONS
PRESSING
QUASI PARTICLES
RADIATIONS
RESONANCE
RESONATORS
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE