CONFIRMATION OF A VANISHINGLY SMALL RING-CURRENT MAGNETIC-SUSCEPTIBILITY OF ICOSAHEDRAL C-60

Abstract

In 1987, Elser and Haddon predicted a vanishingly small pi-electron contribution to the magnetic susceptibility of the icosahedral C60 molecule (buckminsterfullerene). This result runs counter to intuition and was subsequently disputed on the basis of ab initio computations. Following the recent discovery of methods for preparing (and purifying) large quantities of C60, we here report measurements of the magnetic susceptibility, chi, of a solid sample of pure C60 by SQUID magnetometry. The obtained mass value, chi-g = -0.35 x 10(-6), is far below that of graphite or benzene, consistent with the Elser-Haddon picture of accidental cancellation of the diamagnetic and paramagnetic contributions to chi. An estimate of the unusually large paramagnetic contribution is in accord with recent measurements of C60's electronic excitations. The C70 molecule is also measured to have chi-g = -(0.59 +/- 0.05) x 10(-6).