In Situ Rheed and Magneto-Optic Study of Ultrathin Cobalt Films on (111) Gold Substrate: Effect of a Metallic Overlayer
- PDF / 329,621 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 23 Downloads / 139 Views
IN SITU RHEED AND MAGNETO-OPTIC STUDY OF ULTRATHIN COBALT FILMS ON (111) GOLD SUBSTRATE: EFFECT OF A METALLIC OVERLAYER OULD-MAHFOUD S, MEGY R., BARDOU N., BARTENLIAN B., BEAUVILLAIN P., CHAPPERT C. ,** CORNO J., LECUYER B., SCZIGEL G., VEILLET P. and ***W,/ELLER D. Institut d'Electronique Fondamentale and ** Institut d'Optique, Laboratoires associ6s au CNRS, Universit6 Paris-Sud, 91405 Orsay Cedex. *** IBM Almaden Research Center, 650 Harry Road, San Jos6 CA 95120-6099. ABSTRACT We present a comparative in situ RHEED and Polar Magneto-optic Kerr Effect study of the first stages of the growth of a Au overlayer on top of a (111) Co ultrathin film. Drastic behaviours are evidenced on the RHEED diagram, magnetic anisotropy and coercive force, around 1,5 ML of Au coverage. INTRODUCTION A lot of work has been devoted in the last few years to the study of the magnetic anisotropy in ferromagnetic ultrathin films [1]. Besides the magnetocrystalline interface anisotropy introduced by L. N6el [2], strain induced magnetoelastic anisotropy [3], or spin polarization of the interface layer in the non magnetic substrate [41, have been proposed to explain the observed behaviours of anisotropy versus the ferromagnetic film thickness, or for different non magnetic metal substrate. To shed new light on the respective importance of those phenomena, we performed a comparative in situ RHEED and Polar Magneto-optical Kerr Effect (PMOKE) study of a Co ultrathin film deposited on a Au (111) substrate, during the first stages of the growth of the second Co/Au interface with a Au coverage layer. EXPERIMENTAL Details of our sample preparation method have been already published [5]. First a 300 A thick Au buffer layer is grown on a float glass platelet, and annealed to give a polycrystalline, (111) textured, atomically flat film. Co is then deposited at room temperature from an e-beam source, at a rate of about 0.01 A/s. During all evaporation and characterization steps the pressure in the system remains well within the 10-10 mbar range (mostly residual H2 ). Thicknesses are measured using a quartz microbalance, calibrated against Grazing X rays Reflectivity (GXR) measurements performed on test films. GXR was also used as a powerful tool to optimize the quality of the Au buffer layer [6]. We can perform RHEED measurements (up to 30 keV) during film growth. For PMOKE studies, the sample is tilted to face a liquid N2 cooled solenoid, producing a field up to 1.4 kOe, perpendicular to the sample. PMOKE measurements are performed through the clear bore of the coil. To achieve maximum precision and reliability in our study of the magnetic properties versus films thicknesses, we made stepped samples using a moving shutter between sample and evaporation sources. For each sample, up to ten 2mm-wide steps were made, with varying Co or Au coverage thicknesses (resp. tco and tAu). To minimize shadow effects, the shutter slides less than 1 mm below the sample surface, while the sources are more than 450 mm away, with incidence angles less than 8 degrees. I
Data Loading...
