THE CORRELATION BETWEEN STRUCTURE AND MAGNETISM FOR ULTRATHIN METAL-FILMS AND SURFACE ALLOYS

The close correlation between the structure and the properties of ultr athin films can be used to tailor thin films for specific purposes. Fo r metallic films a modification of magnetic properties would be highly desirable. We will discuss such possibilities for films of 3d metals (Cr, Mn, Fe, Co and Ni) and surface alloys formed upon deposition on C u(100) and Ni(100). Especially the weak magnets Fe and Mn exhibit a pr onounced dependence of the magnetic properties on the film structure. Iron films on Cu(100) are a particularly tutorial example of the close correlation between magnetism and structure. Upon room temperature de position, strained fee iron can be stabilized up to 11 monolayers (ML) in two different modifications [1,2]. For thicknesses up to 5 ML, a ( 5 X 1) phase with expanded distances between all interlayers in the en tire Nm is found. This offers a straightforward explanation for the ob served ferromagnetism in this thickness regime. The films show a pecul iar reconstruction pattern, which is indicative for a structural insta bility of the ferromagnetic fee phase [1]. Above 6 ML, Fe films show a ferromagnetic coupling with perpendicular anisotropy at the surface o nly. This surface magnetism is related to an expanded interlayer dista nce at the surface while the interior of the film has a bulk-like fee structure [2]. This behavior is compared with the properties of Mn fil ms and surface alloys formed on Cu(001). The c(2 X 2) surface alloy is stabilized by large magnetic moments of the Mn atoms which are also r esponsible for the pronounced corrugation of the surface layer [3]. Th e concepts employed to understand iron films and Mn/Cu surface alloys will be discussed and generalized.