Free Radicals in K and Rb Admixtured Fullerene C60

J. Stankowskia, W. Kempińskia, P. Byszewskib and Z. Trybułaa aInstitute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland bInstitute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa, Poland

Received: July 12, 1993; in final form: October 11, 1993

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Molecules of C60 form Van der Waals type crystals. The observations reported here concern EPR investigations of such C60 samples with only a slight amount of Rb or K. Detected defects are (C60)+ or (C60)y- ion-radicals. A hole (h) or trapped electron (t) are localized on one fullerene ball. In the case of potassium fullerites C60:K the line shape of EPR signal was of the Dysonian form which is characteristic of conducting electrons in metal. The EPR lines of holes (C60)+ are characterized by gh ≥ g0 whereas for electrons gt is below the value g0 = 2.0023 characteristic of a free electron (gt ≤ g0). The EPR linewidth 2ΔBh1s of the (C60)+ weakly increased with decreasing temperature whereas the EPR linewidth attributed to the electron 2ΔBt1s significantly decreases with decreasing temperature. The C60:K sample reached superconducting phase below Tc = 11 K which is significantly less than Tc = 16.5 K observed for KxC60 where 2 ≤ x ≤ 4.

DOI: 10.12693/APhysPolA.84.1117 PACS numbers: 76.30.Rn, 74.70.Wz