Alkali effects on the electronic states of K3C60 and Rb3C60

✍ Scribed by Katsumi Tanigaki; Mayumi Kosaka; Takahashi Manako; Yoshimi Kubo; Ichiro Hirosawa; Kenshiro Uchida; Kosmas Prassides

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 550 KB
• Volume: 240
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(95)00556-j

✦ Synopsis

The electronic states in metallic alkali fullerides, K,C,, and Rb,C,, are studied in detail by cw-and pulsed-ESR. The ESR linewidth associated with conduction electrons varies substantially, depending sensitively on the alkali metals used. It is clearly revealed that the linewidth is homogeneous and is strongly controlled by the spin-lattice relaxation times (T,)

determined via the spin-orbit interactions of the small fraction of s electrons remaining on the alkali atoms. The results indicate that the electron transfer from the alkali atoms to C,, is not perfectly complete, with the remaining fraction being much greater in the tetrahedral sites than in the octahedral sites of the face-centered cubic lattice.

* Corresponding author.

sistent conclusions must be drawn regardless of the probing methods. Although ESR is the only way to observe directly the nature of the conduction electrons, the data have not been fully understood as yet.

We have carried out detailed continuous wave-(cw) and pulsed-ESR studies on K,C,, and Rb3C,, in order to obtain a more fundamental understanding of these fullerides. In this Letter, we demonstrate that the relaxation times of the conduction electrons are strongly influenced by the alkali metals used, even though the remaining s-electron density on the alkali metals is less than a few percent. This contradicts the simple, but quite generally accepted view since the early days of fullerene research, that the conduction properties in the A,C,, fullerides can be satisfactorily described considering only the partially filled t,,-derived band of C,,.