EPR and magnetism of the nanostructured natural carbonaceous material shungite |
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Authors: | Maria Aldona Augustyniak-Jab?okow Yurii V Yablokov Bart?omiej Andrzejewski Wojciech Kempiński Szymon ?o? Krzysztof Tadyszak Mikhail Y Yablokov Valentin A Zhikharev |
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Institution: | (1) Institute of Molecular Physics, PAS, Smoluchowskiego 17, 60-179 Poznan, Poland;(2) N.S. Enikolopov Institute of Synthetic Polymer Materials, RAS, Profsoyuznaya Str. 70, 117393 Moscow, Russia;(3) Kazan Technological University, Sibirskii trakt 12, 420029 Kazan, Russia |
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Abstract: | The X-band EPR and magnetic susceptibility in the temperature range 4.2–300 K study of the shungite-I, natural nanostructured
material from the deposit of Shunga are reported. Obtained results allow us to assign the EPR signal to conduction electrons,
estimate their number, N
P, and evaluate the Pauli paramagnetism contribution to shungite susceptibility. A small occupation (~5%) of the localized
nonbonding π states in the zigzag edges of the open-ended graphene-like layers and/or on σ (sp
2+x
) orbitals in the curved parts of the shungite globules has been also revealed. The observed temperature dependence of the
EPR linewidth can be explained by the earlier considered interaction of conduction π electrons with local phonon modes associated
with the vibration of peripheral carbon atoms of the open zigzag-type edges and with peripheral carbon atoms cross-linking
different nanostructures. The relaxation time T
2 and diffusion time T
D are found to have comparable values (2.84 × 10−8 and 1.73 × 10−8 s at 5.2 K, respectively), and similar dependence on temperature. The magnetic measurements have revealed the suppression
of orbital diamagnetism due to small amount of large enough fragments of the graphene layers. |
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Keywords: | |
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