Structural, magnetic, and electronic properties of Fe/Au monatomic multilayers.

An Fe/Au monatomic multilayer, consisting of alternating single Fe and Au layers, has been studied by means of the self-consistent full-potential linearized augmented plane wave method. We show by total energy minimization that this artificial thin film is in the tetragonal L10 ordered structure with the ratio of the interlayer spacing to the intralayer lattice constant at 0.865. In this configuration, the magnetic moment in each monolayer, the spin-polarized electronic density of states, and the corresponding band structure are calculated. The results are discussed in connection with recent experiments. PACS numbers: 75.50.Rr, 75.30.Fv, 73.20.Dx Typeset using REVTEX 1 Magnetic multilayers have attracted considerable attention over the past few years [1]. A magnetic monatomic multilayer, consisting of alternating single atomic layers of magnetic and nonmagnetic elements, is the low thickness limit of a magnetic multilayer. One particular structure out of the stacking of alternating single atomic layers is the tetragonal L10 ordered structure shown in Fig. 1. Some ordered alloys are known to have this phase as their naturally occuring structure. For example, an FePt alloy can spontaneously order into the tetragonal L10 structure by a traditional heat treatment [2,3]. More importantly, the recent development of sophisticated growth techniques has made it possible to easily grow quality tetragonal L10 ordered structures that exist naturally [4,5], and to fabricate such materials that otherwise do not exist in nature. One such example is the Fe/Au L10 structure. This structure does not exist naturally in the Fe-Au phase diagram near the equiatomic composition [7], but can be fabricated layer-by-layer by molecular beam epitaxy [8]. This tetragonal L10 ordered FeAu material is of great technological interest because it adds a new member to a family of ferromagnets that may have significant application potential in magnetic recording [9,10]. The magnetic properties of the artificial Fe/Au L10 structure have been characterized experimentally, but to date a complete theoretical study of the system is still lacking. In one previous study, the magnetic properties of the Fe/Au monatomic multilayer were investigated by the layer Korringa-Kohn-Rostoker (LKKR) method [11], but not in the tetragonal L10 ordered structure. In this paper, an Fe/Au in L10 structure was investigated by means of the self-consistent full-potential linearized augmented plane wave method (FLAPW) [12]. We show, by total energy minimization, that this artificial thin film is ferromagnetic in the tetragonal L10 ordered structure. The ratio of the interlayer to the intralayer lattice constant is 0.865, and in this structure the magnetic moment of Fe is 2.75 μB. The spin-polarized electronic density of states (DOS) and the corresponding band structure of the L10 ordered FeAu are also obtained. We discuss these magnetic and electronic properties in connection with the experimental results. The first-principles FLAPW total energy method has been shown to be highly accurate in