INELASTIC EXCHANGE SCATTERING IN ELECTRON-ENERGY-LOSS SPECTROSCOPY - LOCALIZED EXCITATIONS IN TRANSITION-METAL AND RARE-EARTH SYSTEMS

TY - JOUR

T1 - INELASTIC EXCHANGE SCATTERING IN ELECTRON-ENERGY-LOSS SPECTROSCOPY - LOCALIZED EXCITATIONS IN TRANSITION-METAL AND RARE-EARTH SYSTEMS

AU - Porter, S J

AU - Matthew, J A D

AU - Leggott, R J

PY - 1994/7/15

Y1 - 1994/7/15

N2 - Cross sections for quasiatomic excitation by exchange scattering of electrons are calculated in the Born-Ochkur approximation for 3p-3d and 3d-3d transitions in transition-metal systems, and for 4d-4f and 4f-4f transitions in rare earths. The energy dependence of the spin polarization of 3p-3d and 4d-4f losses in reflection electron-energy-loss spectroscopy from ferromagnetic surfaces involves a balance of small-angle spin-dependent inelastic processes accompanied by a high-angle elastic scattering, and large-angle spin-flip exchange scattering without the need for elastic scattering. Both 3d-3d excitations, e.g., in transition-metal compounds, and 4f-4f excitations in rare earths involve spin-flip transitions whose scattering amplitudes g fall off with momentum transfer q such that the full width at half maximum q1/2 (in a.u.) is given by q1/2[r(nl] approximately 2, where [r(nl)] is the expectation value of r for the 3d or 4f electron. The angular width of the spin-flip differential cross section is then much greater than for dipole transitions, a pattern that helps to account for how these intra-atomic transitions compete with dipole processes for primary energies in excess of 100 eV.

AB - Cross sections for quasiatomic excitation by exchange scattering of electrons are calculated in the Born-Ochkur approximation for 3p-3d and 3d-3d transitions in transition-metal systems, and for 4d-4f and 4f-4f transitions in rare earths. The energy dependence of the spin polarization of 3p-3d and 4d-4f losses in reflection electron-energy-loss spectroscopy from ferromagnetic surfaces involves a balance of small-angle spin-dependent inelastic processes accompanied by a high-angle elastic scattering, and large-angle spin-flip exchange scattering without the need for elastic scattering. Both 3d-3d excitations, e.g., in transition-metal compounds, and 4f-4f excitations in rare earths involve spin-flip transitions whose scattering amplitudes g fall off with momentum transfer q such that the full width at half maximum q1/2 (in a.u.) is given by q1/2[r(nl] approximately 2, where [r(nl)] is the expectation value of r for the 3d or 4f electron. The angular width of the spin-flip differential cross section is then much greater than for dipole transitions, a pattern that helps to account for how these intra-atomic transitions compete with dipole processes for primary energies in excess of 100 eV.

KW - GD

M3 - Comment/debate

SN - 0163-1829

VL - 50

SP - 2638

EP - 2641

JO - Physical Review B

JF - Physical Review B

IS - 4

ER -