1 November 1997 Magnetic properties and valence states of fullerene complexes
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As a consequence of the bucky-ball structure of the fullerenes two kinds of fullerene complexes are formed: endohedral and exohedral complexes. The endohedral fullerenes Sc at C82, Y at C82 and La at C82 show ESR spectra with hyperfine splittings resulting from the nuclear spin of the metal ion. Scandium, yttrium and lanthanum are in the 3+ state in the endohedral fullerenes. The situation is more difficult in C82 endohedral metallofullerenes with lanthanides. The situation concerning the valence state of the nedohedral complexes is not yet clear. Magnetic measurements should help to solve this problem Magnetization measurements by means of a SQUID magnetometer did not reveal permanent individual magnetic moments in the case of samarium and ytterbium endohedral fullerene complexes, suggesting the presence of Sm++ and Yb++ ions, respectively. Exohedral fullerene complexes were prepared based on C60 with tetrakisdimethylaminoethylene (TDAE) and with lanthanides. ESR measurements give strong single line spectra without any hint of hyperfine structure interaction of the unpaired electron. SQUID measurements indicate permanent individual magnetic moments in all investigated exohedral complexes, quite unexpectedly also in LaC60. The ferromagnetic ordering of TDAE-C60 at 16 K was studied in detail. Moreover, typical ferromagnetic properties such as magnetic hysteresis, coercivity, remanence and viscosity were found for this exohedral structure at low temperatures.
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Anton Bartl, Anton Bartl, Lothar Dunsch, Lothar Dunsch, Juergen Froehner, Juergen Froehner, Gotthard Seifert, Gotthard Seifert, Dieter Eckert, Dieter Eckert, Manfred Wolf, Manfred Wolf, Karl-Hartmut Mueller, Karl-Hartmut Mueller, } "Magnetic properties and valence states of fullerene complexes", Proc. SPIE 3142, Fullerenes and Photonics IV, (1 November 1997); doi: 10.1117/12.279249; https://doi.org/10.1117/12.279249

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