Magnetic Properties of Fullerene–Thermally Exfoliated Graphite Composites Doped with Sodium

• Published in: Physics of the solid state Vol. 61; no. 10; pp. 1752 - 1758
• Main Authors: Berezkin, V. I., Popov, V. V., Kidalov, S. V., Sharenkova, N. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.10.2019; Springer; Springer Nature B.V
• Subjects: Amorphization; AMORPHOUS STATE; ANGULAR MOMENTUM; BRILLOUIN THEOREM; Buckminsterfullerene; COMPOSITE MATERIALS; CONCENTRATION RATIO; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTAL LATTICES; DOPED MATERIALS; Ferromagnetism; FULLERENES; GRAPHITE; MAGNETIC MOMENTS; MAGNETIC PROPERTIES; Magnetism; PARAMAGNETISM; Physics; Physics and Astronomy; PRESSURE RANGE GIGA PA; QUANTUM NUMBERS; SINTERING; SODIUM; Solid State Physics; TEMPERATURE RANGE; fullerenes; magnetic properties; graphite; carbon composites
• ISSN: 1063-7834; 1090-6460
• DOI: 10.1134/S106378341910010X

The magnetic properties (field range H = 0–50 kOe, temperature range T = 3–300 K), and structural features of a sodium-doped carbon composite material based on fullerene C 60 and thermally exfoliated graphite (TEG) are studied. The material is obtained with different ratios of the components by sintering at a pressure of 7 GPa and T = 600°C, at which it is found that significant amorphization of the crystal lattice of the initial C 60 occurs. The dia-, para-, and ferromagnetic components ( M D , M PM , and M FM ) were separated from the total magnetic moment of the samples under study. It is found that a sodium dopant has no effect on the magnetic properties of the composite. Analysis of the M PM ( H ) field dependences by using the Brillouin function for the fullerene-containing sample (i.e., without TEG) makes it possible to determine the quantum number of the total angular momentum of paramagnetic (PM) centers. Its value is found to be J = 1, which corresponds to elementary magnetic moment μ PM = 2μ B of a PM center. The concentration of PM centers is estimated at the level of N PM ≈ (2–5) × 10 18 g –1 for most samples, including the material without TEG. The introduction of TEG into the initial composition and an increase in its proportion in the composite leads to a strong increase in the magnetic moment, which is explained by an increase in both the J value and the concentration of PM centers.