THE BAND-STRUCTURE OF CHEMICALLY ORDERED CO3PT

Owing to surface diffusion, the molecular beam epitaxy (MBE) technique has made it possible to produce new binary alloy films by coevaporati on on a single-crystal substrate in an ultrahigh vacuum. In this fashi on, a hexagonal close-packed (hcp) structure of the Co3Pt compound wit h ferromagnetic and chemical order has been discovered recently which was not previously known in the bulk alloy equilibrium phase diagram. Using a tight-binding linear muffin-tin orbital (TB-LMTO) method for t he electronic structure of Co3Pt, we treat first the reference case of the fee L1(2) phase and then the hcp phase. In this last phase we con sider both the standard DO19 structure and a modified version of it. W e perform the band-structure calculation in both the paramagnetic and ferromagnetic cases, and on the basis of a total energy calculation we arrive at the conclusion that the ferromagnetic phase of the DO19 str ucture is the most stable.