Ab initio study of hexagonal Fe/Ru multilayers

Calculations of structural and electronic properties of hexagonal Fe/Ru multilayers, as well as of pure Fe and Ru metals, were performed using the spin-polarized density functional technique. Apart from the conventional hexagonal AB stacking of close-packed planes, an AB? stacking with atoms in a B? plane shifted over the triangle edges formed by atoms in an A plane was examined in the Fe part of the multilayers. It was concluded that the most stable solution is a ferromagnetic configuration with an AB? stacking within Fe layers with the axial ratio cFe/aRu = 1.47 and with an AB stacking in Ru layers with cRu/aRu = 1.60. Interfacial interdiffusion effects and antiferromagnetic order were also investigated in connection with the reported disappearance of a magnetism at the Fe/Ru interfaces. The equilibrium lattice parameters of hexagonal close-packed Fe metal, aFe = 2.44 Å, cFe/aFe = 1.60, were obtained for a nonmagnetic state. At an only slightly larger lattice constant an antiferromagnetic state appears. For bulk Ru the parameters aRu = 2.73 Å, cRu/aRU = 1.58 were found for a nonmagnetic phase with the onset of antiferromagnetism beginning at highly dilated interatomic distances. Œ 2001 American Institute of Physics.