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Abstract:
We report on theoretical investigations of the exotic magnetism in
rubidium sesquioxide Rb(4)O(6), a model correlated system with an open
2p shell. Experimental investigations indicated that Rb(4)O(6) is a
magnetically frustrated insulator. The frustration is explained here by
electronic structure calculations that incorporate the correlation
between the oxygen 2p electrons and deal with the mixed-valent oxygen.
This leads to a physical picture where the symmetry is reduced because
one third of the oxygen in Rb(4)O(6) is nonmagnetic while the remaining
two thirds assemble in antiferromagnetic arrangements. A degenerate,
insulating ground state with a large number of frustrated noncollinear
magnetic configurations is confidently deduced from the theoretical
point of view. These findings demonstrate in general the importance of
electron-electron correlations in open-shell p-electron systems.
