Magnetic Order of Fe and Co on Cu(001)
- PDF / 346,494 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 8 Downloads / 186 Views
MAGNETIC ORDER OF Fe AND Co ON Cu(001) A. HAROUN*, A. CHOUAIRI*, S. OUANNASSER*, P.J. JENSEN**, K.H. BENNEMANN**, AND H. DREYSSE* *Laboratoire de Physique du Solide. BP 239, F-54506 Vandoeuvre-les Nancy, France. ** Institut fUr Theoretische Physik, Freie Universitdit Berlin. Arnimallee 14, D- 1000 Berlin 33, Germany. ABSTRACT We determine the initial growth mode of Co and Fe on Cu(001). In the monolayer range Co and Fe present a clear trend to form clusters on Cu (001). Supposing a perfect epitaxy and fcc lattice, the magnetic moment distribution is determined by using a tight binding Hubbard-like Hamiltonian. The influence of the temperature is taken into account in order to compare the theoretical predictions with experimental results.
INTRODUCTION The skill of elaboration process and the development of experimental techniques have revealed the complexity of epitaxially grown transition metal systems. In this work we concentrate on the magnetic properties of very thin Co and Fe films on a Cu(001) substrate. These systems show controversial experimental results. At room temperature for a Co monolayer on Cu(001), Pescia et al.[1J found a long range ferromagnetic order, while Schneider et al.[21 have shown that the Curie temperature is below 50K. For Iron conflicting results have been reported [3]. The key quantity is the preparation temperature: for low preparation temperature, five monolayers of fcc-Fe(001) show a large magnetic moment, while after annealing at temperatures above 500K a transition to state with a low moment is observed [4]. Concerning the growth mode of Co on Cu(001) substrate, A.Schmid[5] showed by using STM that roughly 30% of the Cu surface is still not covered by the first layer of Co when 10% of the second layer is already present on top of the first layer islands, in agreement with the results of Li and Tonner [6]. For the Fe/Cu system, the situation is confusing . Layer by layer growth mode has been found [7,8], whereas Chambers et al. [9] observed that at room temperature the first monolayer of Fe does not adsorb uniformely, but forms two-layer thick clusters. At 300K Thomassen et al. I10] have observed a layer by layer growth mode for thickness above 5 ML, but below this thickness the film is characterized by iron agglomeration. In this short paper we intend to study the growth mode of Fe, Co, and Ni on Cu(001), and to discuss the influence of the temperature on the magnetic behavior of these systems. A more complete discussion of the magnetic properties of Co and Fe layers on Cu(001) is in progress and will reported elsewhere. INITIAL GROWTH MODE OF Co AND Fe ON Cu(001). The initial growth mode of Co and Fe on Cu(001) can be estimated with a simple approach. Consider in the monolayer range, on top of the Cu(001) semi-infinite crystal, a binary alloy (adsorbed atoms and vacancies) on a square lattice: Similarly to the bulk alloy phase stability studies [1 I] this alloy problem can be transformed to a two-dimensional "Ising-like" problem. Hence, each lattice site p is associated with a ps
Data Loading...
