Magnetic Properties of FE X MN 1-X /IR(100) Superlattices.
- PDF / 336,782 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 60 Downloads / 180 Views
ABSTRACT We have produced pseudomorphic FexMnltx/Ir(100) superlattices having different stoichiometry (0.8 > x > 0.3). The alloy crystalline structure is body centered tetragonal with a c/a ratio between 1.18 and 1.26. Iron rich alloys are ferromagnetic when the corresponding bulk alloys are antiferromagnetic. Manganese rich alloys are certainly antiferromagnetic according to bulk magnetization measurements and Mbssbauer effect results. The transition from a ferromagnet with a vanishing moment when x = 0.5 to an antiferromagnet is associated with a volume expansion.
INTRODUCTION: The elaboration of epitaxial new phases of transition metals offers unique opportunities to study the relationship between crystalline structure and magnetism [I]. During the recent years, we have studied the properties of body centered tetragonal iron on (001) Iridium. The main result of this study [2] is the appearance of a magnetic moment at a critical volume of about 0.012 nm 3 . This volume is very close to the prediction of appearance of magnetism in fcc iron [3]. Manganese is also an attractive transition metal since some theoretical work [4,5] have predicted the possibility of having a ferromagnetic phase with a large magnetic moment in the body centered cubic phase of manganese. However, despite a lot of work (see eg[6]), no one has succeded in producing bcc manganese. Moreover, the body centered tetragonal phases realised by several
workers [6] seems to be antiferromagnetic as explained by Oguchi and Freeman [7]. We try another route to have ferromagnetic manganese. Since we have grown ferromagnetic iron on Ir (001) and non magnetic (or antiferromagnetic) manganese on the same Ir (001)[8], we believe that in the Fe×Mnl-x alloys on Ir (001) we must have somewhere a magnetic transition between ferromagnetism and antiferromagnetism. The goal of this paper is to investigate this possibility.
GROWTH AND STRUCTURE Using MBE technique, we have grown FexMnli, with 0.8 > x _>0.3 on Ir(100). A thick buffer layer of Ir(100) was first grown on (100) MgO. The growth of the alloys on Ir is pseudomorphic, layer by layer with RHEED oscillations up to about 20 atomic planes at room temperature and up to 10 atomic planes at 100°C. The atomic planes present then a square symetry and a parameter equal to 0.2715 nm. We have studied pseudomorphic superlattices of about 9 atomic planes of FexMni-x alloys and 2 nm of Ir. The exact thicknesses of the superlattices components was determined by Small Angle X-Ray Reflectivity. Results of the simulation of the reflectivity spectra are reported in table I, t is the thickness and a the roughness of the interfaces. The results of reflectivity were confirmed by cross section transmission electron microscopy. The crystalline structure of these superlattices was determined by X- Ray Scattering. We have fitted the diffraction results with a model taking into account a plane of intermediate concentration at the interfaces. We have deduced from the fits the structural parameters reported in table II. One 271 Mat.
Data Loading...
