.3 D Metal Ultra-thin Film Structure And Magnetic Properties

With the development of the experiment technology and theory, the research of the ultrathin magnetic films has made much progress in last decade. Lots of manufactured structure such as two-dimensional film, one-dimensional line and zero-dimensional dot has attracted more and more attentions. The deeply understand of the properties of low dimensional magnetic structures is useful both to the fundamental physics and to the new progress of commercially application in spintronics. In this thesis, I mainly introduce my recent work about the structure of Cr films growth on GaAs(001) surface, the spin density wave of fee Fe on Cu(100), magnetism of bcc Ni on GaAs(001), interface magnetism of Co/Pd(100) epitaxied by Pulse Laser Deposition.1. Growth of Cr thin films on GaAs(001) was carried out using Molecular Beam Epitaxy and was investigated by in situ reflection high-energy electron diffraction (RHEED) and ex situ X-ray diffraction (XRD). The results show that there are two competing mechanisms during the growth, and the film structure strongly depends on the growth temperature. The single-crystalline Cr films with the body-centered-cubic (bcc) structure are obtained, with the epitaxial relationship of (0 0 1)[0 0 l]||Cr(0 0 1)[001] GaAs and (001)[100]Cr(001)[100]GaAs .2. For Fe films epitaxially grown on Cu(100) at 300 K, the total magnetic moment as a function of film thickness and its temperature dependence have been investigated in situ with a multi-technique approach. The results exclude the collinear type-1 antiferromagnetic configuration as the magnetic structure for face-centered cubic (fee) Fe films on Cu(lOO). It is proposed that a spin-density-wave (SDW) state is responsible for the magnetic structure. Based on the accurate thickness calibration, the borderlines of the three well-known regions with distinct magnetic properties are determined unambiguously for Fe films on Cu(100). A theoretically predicted temperature driven martensitic phase transition between regions II and III is indeed confirmed in experiment.3. The single-crystalline Ni film with the body-centered-cubic(bcc) structure are obtained epitaxially on GaAs(001) surface at 170K. The in-plane and out-of-plane lattice constant of Ni/GaAs(100) was determined X-ray diffraction. And the magnetic properties and electron structure of bcc Ni have been studied with MOKE, FMR, SQUID, and Angle Resolved Photoemission.4 Ultrathin Co films epitaxially grown on Pd(100) by Pulse Laser Deposition(PLD) and by normal Thermal Deposition(TD) was investigated respectively by in situ MOKE and Optical Ellipticmeter. The result demonstrates that the magnetic property strongly depends on interface condition. Magnetic-optical Kerr signal decreases abnormally in the PLD Co/Pd when Co is thicker than about1ML. The total magnetic signal reach the minimum at about 1.3~1.4ML and then again increased linearly with the increasing of Co film thickness.