Local Spin Polarization at Surfaces Probed by Hollow Atoms

Abstract

The relaxation of hollow atoms produced by slow multiply charged ions impinging on surfaces produces characteristic Auger electron spectra. These spectra, which serve as fingerprints of the interaction, can be used to probe local spin ordering at surfaces by relating changes in the intensities of different spin states to local spin polarization at the surface. The area from which the electrons are captured is of the order of a few Angstrom(2), only. The potential of the method is illustrated by He(2+) and N(6+) ions interacting with a ferromagnetic Ni(110) crystal. From the Auger spectra we determine a spin polarization of approximately 90% at room temperature.

A low energy ion source for electron capture spectroscopy

“…For instance, a direct comparison of the neutralization of He 2 + and He* + (2s) in the same experiment could provide improved insight to the mechanism of the spin-dependent capture of two electrons from a surface, and the interpretation involved. 7,8 In contrast, operation at high acceleration voltages leads to a pure He + (1s) beam with no detectable (2s) contribution. This can be particularly useful for the selective investigation of different paths in the neutralization of the helium ions.…”

“…5,6 The capture of two electrons into the singlet a) Electronic mail: tusche@mpi-halle.mpg.de or triplet terms of He** is detectable by the energy of the auger electrons emitted during the relaxation, and was discussed as a local probe of spin polarization. 7 Related to the high surface sensitivity, interpretation of the results, however, is complicated by subtle changes to the surface electronic properties. 8 In the static picture, the available energy for the emission of electrons equals the ionization potential of the primary particle.…”

Highly-charged-ion-induced electron emission from C60thin films

“…The general trends of neutralization and relaxation mechanisms of such HCIs interacting with a surface are described by the hollow-atom scenario [1][2][3][4][5]. A key ingredient in this scenario is the electronic structure [2,[6][7][8][9] of the surface and especially the work function. A possible way to tune the work function of a surface is by means of thin-film deposition.…”

Studies on Auger Neutralization of He + Ions in Front of Metal Surfaces

“…Recently, it was suggested to make use of the neutralization of He 2 þ ions in order to obtain information on the (short range) magnetic ordering of ferromagnetic surfaces [37]. It turns out, however, that the neutralization scenario of He 2 þ in front of metal surface is too complex in order to obtain clear-cut information on magnetic properties.…”