X-ray photoelectron diffraction studies of structural and magnetic disordering transitions near surfaces
This thesis deals with order/disorder transitions near solid surfaces as studied by x-ray photoelectron diffraction and photoelectron holography. Transitions involving both atomic positional order and magnetic order have been studied. Further evidence for a reversible high-temperature surface-disordering phase transition on Ge(111) has ben found using Ge 3p x-ray photoelectron diffraction (a short-range-order probe of surface structure) and photoelectron holography. Azimuthal diffraction data at takeoff angles with respect to the surface of [theta] = 19[degrees] and [theta] = 55[degrees] show abrupt drops in intensity of [approximately]30%-40% over the temperature interval of 900-1200 K. Photoelectron holographic near-neighbor images at temperatures below and above the transition region furthermore indicate an identical near-neighbor structure for all atoms present in ordered sites. These combined diffraction and holography data show that by 1200 K, the Ge(111) surface is covered by a completely disordered overlayer of about 2 Ge monolayers in thickness. The rate of growth of this overlayer with increasing temperature is in excellent agreement with recent medium-energy ion scattering results, although the thickness found for the overlayer is 1.5-2.0x larger than that derived from ion scattering. Based on these data, a disordering model for the Ge(111) surface phase transition occurring at 1050 K is discussed. Spin-polarized photoelectron diffraction is a recently developed and promising application of photoelectron diffraction to the study of the magnetic structure near surfaces. This technique is based on an internal source of spin-polarized electrons as produced in core-level multiplet splittings and it is thus sensitive to the short-range magnetic order around a given type of emitter in the crystal. In this thesis, data on MnO have been extended to include the use of synchrotron radiation at photon energies of 150, 170, and 190 eV.
- Research Organization:
- Hawaii Univ., Honolulu, HI (United States)
- OSTI ID:
- 7045521
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GERMANIUM
MAGNETIC PROPERTIES
PHASE TRANSFORMATIONS
SURFACE PROPERTIES
ANTIFERROMAGNETIC MATERIALS
FERROMAGNETIC MATERIALS
GADOLINIUM
IRON
MANGANESE OXIDES
PHOTOELECTRON SPECTROSCOPY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 1000-4000 K
CHALCOGENIDES
ELECTRON SPECTROSCOPY
ELEMENTS
MAGNETIC MATERIALS
MANGANESE COMPOUNDS
MATERIALS
METALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTHS
SPECTROSCOPY
TEMPERATURE RANGE
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
360102* - Metals & Alloys- Structure & Phase Studies