Spin-polarized Electron Emission Spectroscopy Research Articles

Magnetic studies of bct Fe(100)p(1 × 1)/Pd(100) films

Electron capture (ECS) and spin-polarized electron emission spectroscopy (SPEES) studies are performed at surfaces of ultra-thin bct Fe(100)p(1 × 1) films deposited on atomically flat Pd(100) substrates. For well-annealed films, the electron spin polarization (ESP) is oriented in-plane, and ferromagnetic order sets in at a surface Curie temperature T Cs = 662.3 K (4 ML). Near T Cs, the ESP follows the power law ( T Cs — T Cs) β, with a critical exponent β = 0.129 ± 0.01 evaluated near T Cs. Varying the probing depth, it is found that the layer-dependent average (ESP) at the topmost surface layer (37%) is enhanced by 32% as compared to that of bulk layers (28%). Pd Auger electrons emitted from the Fe/Pd interface are spin polarized with their ESP oriented parallel to that of emitted Fe Auger electrons.

Electron capture and emission spectroscopy to study surface and interface magnetism

Electron capture spectroscopy (ECS) and spin-polarized electron emission spectroscopy (SPEES) are extremely sensitive techniques to probe surface magnetic properties. Ultra-thin bct Fe(100)(1×1)/Pd(100) films exhibit 2D Ising critical behavior. The surface electron spin polarization (ESP) follows precisely the exact solution of the 2D Ising model as given by Yang. The average magnetization of the topmost surface layer is enhanced by 32% compared to that of bulk layers. Pd Auger electrons emitted from the Fe/Pd interface are spin-polarized, and the ESP is oriented parallel to that of emitted Fe Auger electrons. At surfaces of 5nm thick hcp Tb(0001)/W(110) films, strong surface magnetic surface anisotropies are found. The onset of ferromagnetism occurs ≈30 K above the bulk Curie temperature (220K) of Tb. For clean Fe and Fe/Pd surfaces, the ESP of low-energy (≈2 eV) emitted electrons is substantially enhanced by Stoner excitations. The existence of a nonzero ESP at O/Fe surfaces demonstrates the absence of a magnetically dead surface layer.

Spin-polarized electron emission spectroscopy (SPEES) to study particle-surface interaction mechanisms

The surface magnetic and electronic properties of magnetic (Fe, Ni(110)) and nonmagnetic (Al, Pd(100)) metals are investigated using spin-polarized electron emission spectroscopy (SPEES). We find that the energy distribution of electrons emitted during grazing-angle ion-surface scattering exhibits pronounced peaks containing fundamental information on ion-surface interaction mechanisms. These new structures can be explained in terms of various ion-induced electron excitation processes occurring at the very surface.

Probing the Surface-Vacuum Interface with Spin-Sensitive Metastable Atom Deexcitation, Electron Capture and Electron Emission Spectroscopies

ABSTRACTSpin-Polarized Metastable Atom Deexcitation (SPMDS) and Electron Capture (ECS) Spectroscopies probe the exponential tails of electronic wavefunctions extending from the surface into the vacuum, and are consequently extremely sensitive to the surface-vacuum interface. The use of SPMDS to probe the near-surface vacuum magnetization of Ni (l 10) and Fe (l 10) and the dramatic changes that result upon exposure to ambient gases is discussed, as is the use of ECS and Spin-Polarized Electron EMission Spectroscopy (SPEES) to determine the ferromagnetic and critical behavior of surfaces and ultra-thin epitaxial systems.

Spin-polarized electron emission spectroscopy (SPEES) at Ni(110) and PtMnSb surfaces

We have shown that using grazing-angle scattering of H + and He + ions at atomically flat surfaces of well characterized Ni(110) picture-frame single crystals and polycrystalline PtMnSb samples exhibit spin- and energy-dependent electron spectra which show a dramatic difference compared to that of traditional secondary electron spectra. We studied the energy- and spin-resolved intensity distribution of electrons, emitted along the surface normal. The distinct peak structure of the energy spectrum, which lacks a strong secondary electron background, allows us to compare our data with available theoretical data on the electronic structure of Ni(110) and PtMnSb. We further obtain important information on particle-surface interaction mechanisms.

Ion-induced emission of spin-polarized electrons to study surface magnetism

A novel technique, ion-induced, angle- and energy-resolved, spin-polarized electron emission spectroscopy (SPEES) has been used to probe the electron spin polarization (ESP) at the surface of Ni(110) picture-frame single crystals which are well characterized using AES, LEED, RHEED and STM. The energy distribution of the emitted electrons (0–70 eV), which includes spin-polarized Auger electrons, is significantly different from that of electron-induced secondary electrons and contains fundamental, spin-dependent information on the local surface magnetic structure of Ni(110).

Angle- and energy-resolved, spin-polarized electron emission spectroscopy to study surface magnetic and electronic properties.

We report on a new technique, spin-polarized electron emission spectroscopy. Using grazing-angle, surface scattering of H + and He + ions at Ni(110), we find that the angle-resolved energy distribution of emitted spin-polarized electrons is significantly different from that of electron-induced secondary (cascade) electrons and exhibits a series of characteristic «peaks» (including element-specific Auger electrons). We obtain characteristic, spin-dependent information on the surface electronic structure of Ni(110) and on atom-surface charge-transfer processes

Capture and emission of spin-polarized electrons to study surface magnetism and critical behavior

Using angle- and energy-resolved, spin-polarized electron emission Spectroscopy (SPEES) and electron capture Spectroscopy (ECS), the long-ranged and short-ranged surface electron spin polarization (ESP) of Fe 80B 20, Ni(110) and Tb(0001)/W(110) films is investigated. All surfaces are well characterized using AES, LEED, RHEED, STM and ion surface reflection (ISR). Nonzero ESP is found at all magnetized surfaces. For Tb(0001)/W(l10), near the surface Curie temperature T Cs, surface-enhanced long-ranged magnetic order and novel critical behavior is found. Short-ranged magnetic order exists above T Cs. The angle-resolved energy distribution of grazing-angle , ion-induced (H + and He + ions) emitted electrons (0–70 eV), which exhibits a series of pronounced “peaks” including spin-polarized and element-specific Auger electrons, is strongly different from that of electron-induced secondary electrons and contains fundamental information on the surface magnetic structure of Ni(110) and on the spin dependence of various electronic transition processes occuring at magnetic surfaces.

Novel studies of spin-polarized electrons emitted during grazing incidence ion reflection at magnetic surfaces

Using a new technique, spin-polarized electron emission spectroscopy (SPEES) and electron capture spectroscopy (ECS), the electron spin polarization (ESP) at the topmost surface layer of ferromagnetic materials is investigated. All surfaces are well characterized using AES, LEED, RHEED and STM. Nonzero ESP is found at remanently magnetized surfaces of atomically clean, amorphous Fe 80B 20 and (110)-surface-oriented Ni picture-frame single crystals. The angle-resolved energy distribution of the ion-induced emitted electrons is strongly different from that of electron-induced secondary electrons and contains most valuable information on the surface magnetic structure of Ni(110) and on the spin dependence of various electronic transition processes occurring at surfaces. The ESP of electrons (energies between 9 and 12 eV) emitted during grazing-angle ion reflection amounts to + 5.5% which is close to the total net Ni-magnetization of +5.6%.