Abstract
We perform density-functional calculations of the magnetic properties of a simplified structure aimed at capturing some of the features of the elusive phase of molecular oxygen at high pressure. Starting with the phase—which is a quasi-two-dimensional distorted triangular arrangement of antiferromagnetically ordered molecules—pressure could decrease the ratio in the basal planes pushing it toward the ideal triangular value of thus increasing magnetic frustration. We conjecture that when frustration takes over, the magnetic order may turn into a planar spin-spiral structure inside the phase, until at higher pressures band-overlap metallization suppresses magnetization in the phase. This conjecture is substantiated by calculations that also represent the attempt to apply state-of-the-art pseudopotential techniques to the magnetic properties of a frustrated antiferromagnet.
- Received 11 June 1999
DOI:https://doi.org/10.1103/PhysRevB.61.6145
©2000 American Physical Society