SPLEEM

Unconventional magnetisation texture in graphene/cobalt hybrids

Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent already a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism.

Spin-resolved inelastic mean free path of slow electrons in Fe

The spin-dependent reflectivity of slow electrons from ultrathin Fe films on W(110) has been measured with spin polarized low energy electron microscopy. From the amplitude of the quantum size oscillations observed in the reflectivity curves the spin-dependent inelastic mean free path (IMFP) of electrons in Fe has been determined in the energy range from 5 to 16 eV above the vacuum level. The resulting IMFP values for the spin-up electrons are clearly larger than those for the spin-down electrons and the difference between the two values decreases with increasing electron energy in agreement with theoretical predictions.

Trends in low energy electron microscopy

Low energy electron microscopy (LEEM) and spin polarized LEEM (SPLEEM) are two powerful in situ techniques for the study of surfaces, thin films and other surface-supported nanostructures. Their real-time imaging and complementary diffraction capabilities allow the study of structure, morphology, magnetism and dynamic processes with high spatial and temporal resolution. Progress in methods, instrumentation and understanding of novel contrast mechanisms that derive from the wave nature and spin degree of freedom of the electron continue to advance applications of LEEM and SPLEEM in these areas and beyond. We review here the basic imaging principles and recent developments that demonstrate the current capabilities of these techniques and suggest potential future directions.

Cathode lens electron microscopy: past and future

This retrospective sketches the evolution of emission electron microscopy, low energy electron microscopy and related methods from the early stages up to the present state and gives a brief outlook on the future possibilities of these cathode lens electron microscopy techniques. It is concerned mainly with instrumentation, discusses some little known work and emphasizes important steps in the evolution of the field instead of attempting to review it in detail.

Strain engineering of magnetic anisotropy in thin ferromagnetic films

Magnetic properties of iron films grown on Au layers with different thicknesses on a W(110) surface are studied with spin polarized low energy electron microscopy. The iron thickness for the onset of ferromagnetic order depends approximately linearly on the thickness of underlying gold film. The easy axis direction also depends upon the Au thickness. It is parallel to the tungsten [Formula: see text] direction at the onset of magnetization for one and two monolayers of gold. For thicker gold films the easy axis is parallel to the [001] direction. The direction of the easy axis and the onset of ferromagnetic order are discussed in terms of magnetic anisotropies, interaction between the iron overlayer, gold and tungsten substrate, Fe film strain and morphology.

Surface microanalysis with slow electrons

Microanalysis on the 10-nm level using imaging, diffraction, and spectroscopy of slow photo-emitted and reflected electrons is discussed. The instrumentation that uses a cathode lens is briefly reviewed, and a number of applications illustrate the power of this microanalysis method.