RESEARCH AND DEVELOPMENT ON ADVANCED GRAPHITE MATERIALS. VOLUME XX. THE ELECTRIC AND MAGNETIC PROPERTIES OF PYROLYTIC GRAPHITE
A study was made of the electric and magnetic properties of a series of highly turbostratic pyrolytic graphite deposits. The diamagnetic susceptibility, Hall coefficient, and electron spin resonance g value are observed to have much larger magnitudes than corresponding measurements made on single crystals of graphite. The results are interpreted as being due to the turbostratic character of the deposit which brings about a decreased interaction between the randomly rotated graphitic planes. The overlap of the electron and hole bands is thereby reduced and as a first approximation one can interpret the results using the simple two dimensional model of Wallace. McClure's diamagnetism formula, which is based on the Wallace model, yields a maximum trace value of --39 emu/g. The largest observed value is --33.5 emu/g, a diamagnetism almost 50 per cent greater than the nornual single crystal value of -22.8 emu/ g. To obtain from theory the large variation of g shift and diamagnetism as a function of formation temperature, it is necessary that acceptors be present whose concentration decreases as the temperature of formation increases. Similar acceptors have been postulated by others to explain the properties of high temperature carbons. (auth)
- Research Organization:
- National Carbon Co., Parma, Ohio
- DOE Contract Number:
- AF33(616)-6915
- NSA Number:
- NSA-18-007219
- OSTI ID:
- 4118754
- Report Number(s):
- WADD-TR-61-72(Vol.XX)
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- United States
- Language:
- English
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