Electronic states in Rb 1 C 60 studied by EPR under pressure: 3D Mott-Hubbard system

Electron paramagnetic resonance (EPR) is applied to orthorhombic ${\mathrm{Rb}}_{1}{\mathrm{C}}_{60}$ 1D polymer under hydrostatic pressure. The EPR linewidth is interpreted in terms of Elliott mechanism. EPR signal intensity provides us the antiferromagnetic transition temperature ${T}_{\mathrm{N}}$ where the intensity drops suddenly. Finally, a phase diagram of the electronic states in $o{\ensuremath{-}\mathrm{R}\mathrm{b}}_{1}{\mathrm{C}}_{60}$ is constructed from ${T}_{\mathrm{N}}$ vs pressure diagram, along with the resistivity under pressure, reported by Khazeni et al. [Phys. Rev. B 56, 6627 (1997)]. From this diagram we can definitely conclude that $o{\ensuremath{-}\mathrm{R}\mathrm{b}}_{1}{\mathrm{C}}_{60}$ is not a SDW system typical for 1D electronic band, but a 3D Mott-Hubbard insulator near a border of the transition.