Orientational order in A3C60: antiferromagnetic Ising model for the FCC lattice.

Mazin I.I., Liechtenstein A.I., Gunnarsson O., Andersen O.K., Antropov V.P., Burkov S.E.

By analysis of the electronic contribution to the binding in A3C60, the authors show that the problem of orientational ordering can be mapped onto the FCC nearest-neighbor antiferromagnetic Ising model with J at the order of 100 K. For T<1.76 J, the system should be found in a state which is antiferromagnetically ordered in two dimensions and disordered in the third. This is not inconsistent with present X-ray powder data. The authors find that the low-temperature conduction-band structure closely resembles that of the simplest antiferromagnetically ordered (so-called bidirectional) crystal.

Physical Review Letters, 70 4142-5, 1993.

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