Itinerant electrons and magnetism in the Co-C chain compound YCoC

Density-functional studies of the electronic structure of the Co-C linear-chain compound, YCoC are reported. The band structure near the Fermi energy shows a mixture of rather heavy Co-d-derived bands, and near-one-dimensional dispersive bands associated with the bonding of the Co-C chains. The resulting density of states is high, yielding an extremely weak ferromagnetic instability via the Stoner mechanism. However, the Fermi surfaces are strongly nested, suggesting competing antiferromagnetic spin fluctuations. An interesting possibility is that in clean samples a renormalized paramagnetic ground state may emerge, due to the combination of the weak competing ground states, the near one dimensionality of the bands, and quantum fluctuations.