Electronic localization in Rb4C60 from bulk magnetic measurements
Abstract
The dc-magnetization measurements were performed between 50 G and 40 kG using a superconducting quantum interference device magnetometer on powder samples of Rb4C60. The magnetic susceptibility reveals thermally activated behavior with an activation energy of 1200+/-100 K and a diamagnetic temperature-independent part χd=-3×10-4 emu/mol. By calculation of the related magnetic moments and by comparison with the NMR and EPR data we conclude that the additional electrons are localized on the C60 molecule and form a spin-singlet ground state. The temperature-dependent paramagnetism is due to thermally excited electrons. Strong electron correlations and lattice distortions (crystal field or/and Jahn-Teller effect) are discussed as a possible origin for the lowest unoccupied molecular orbital (LUMO) level splitting and for gap formation. The experimental results are in good agreement with the existence of Jahn-Teller or crystal-field distortions, providing the t1u LUMO level degeneracy is lifted.
- Publication:
-
Physical Review B
- Pub Date:
- February 1995
- DOI:
- 10.1103/PhysRevB.51.3978
- Bibcode:
- 1995PhRvB..51.3978L
- Keywords:
-
- 61.46.+w;
- 71.70.-d;
- 33.15.Kr;
- Level splitting and interactions;
- Electric and magnetic moments polarizability and magnetic susceptibility