The magnetic properties of surfaces are now being explored with electron spectroscopies that use electron spin polarization techniques. The increased activity in surface magnetic measurements with polarized electron beams is spurred by new scientific and technological challenges and is made feasible by recent advances in the technology of sources and detectors of polarized electrons. The ability to grow thin films and to engineer artificial structures permits new phenomena to be investigated at magnetic surfaces and interfaces. For such investigations, spin-polarized electron techniques—such as polarized electron scattering, polarized photoemission, polarized Auger spectroscopy, and scanning electron microscopy with polarization analysis—have been and will probably continue to be used to great advantage.

Polarized Electron Probes of Magnetic Surfaces

Surface magnetic structure analysis of Ni(001) by polarized electron diffraction

Publisher Summary This chapter describes the rich variety of spin, dependent phenomena in various areas of solid state and surface physics. Spin–polarized (SP) electrons seemed an elusive rarity, and the effects of exchange and spin orbit coupling appeared to be a small, mostly negligible correction to the dominant effects produced by the Coulomb field of the electrons. The experimental techniques used in the production of spin–polarized electron beams, measurement of SP, and various types of experiments with polarized electrons, such as photo or field emission of electrons are discussed. SP of the total photoelectron current versus photon energy is graphically represented. Magnetism in metals, magnetism in systems with localized magnetic moments, and the symmetry of electronic states is also reviewed. The spin dependence of the elastic scattering of the electrons from solids is performed by spin-polarized LEED (SPLEED) experiments. SP photoemission can be used as a surface magnetometer to monitor surface segregation and chemical reactions at the surface. Surface magnetization curves are obtained with the external magnetic field applied parallel or perpendicular to the surface.

Spin-Polarized Electrons in Solid-State Physics

https://pub.uni-bielefeld.de/download/1783067/2314116/mueller_14.pdf

Spin polarization in low-energy electron diffraction: surface analysis of Pt(111) [Abstract]

Exchange and spin-orbit scattering asymmetries of spin-polarized low-polarized low-energy electrons from Fe(110) are measured at room temperature for several beams at constant energies as functions of the polar angle of incidence (“rocking curves”). Corresponding calculations by means of a relativistic multiple scattering formalism gave results in good agreement with the experimental data. The sensitivity of part of the calculated curves to changes in the layer magnetization implies an enhancement of the topmost layer magnetization by about 36 to 40% relative to the bulk and possibly a reduction in the second layer. Further, a dominance of spin-down over spin-up inelastic scattering is deduced associated with 3p 3d excitation.



Die durch Austauschwechselwirkung und Spinbahnkopplung bedingten Streuasymmetrien bei der Beugung langsamer Elektronen an Fe(110) werden bei Zimmertemperatur fur verschiedene Strahlen bei konstanter Energie als Funktionen des polaren Einfallswinkels gemessen. Entsprechende Rechnungen mittels eines relativistischen Vielfachstreuformalismus liefern Ergebnisse in guter Ubereinstimmung mit den experimentellen Daten. Aus der Empfindlichkeit von Teilen der berechneten Kurven gegenuber Anderungen der schichtabhangigen Magnetisierung folgt eine Erhohung der Magnetisierung der obersten Schicht um ca. 36 bis 40% relativ zum Volumenwert und moglicherweise eine Verringerung in der zweiten Schicht. Auserdem folgt, das bei der 3p 3d-Anregung Minoritatselektronen starker inelastisch gestreut werden als Majoritatselektronen.

H. Pleyer

Papers

On the feasibility of studying surface magnetism by spin-polarized low-energy electron diffraction