AVS 55th International Symposium & Exhibition
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThM

Paper MI-ThM1
Exchange-Split Surface State on Gd(0001) Revisited

Thursday, October 23, 2008, 8:00 am, Room 206

Session: Magnetic Surfaces, Interfaces, Thin Films and Heterostructures
Presenter: M. Budke, WWU Münster, Germany
Authors: M. Budke, WWU Münster, Germany
M. Donath, WWU Münster, Germany
Correspondent: Click to Email

Gd is considered to be a prototype Heisenberg ferromagnet, because its magnetism originates from the strongly localized electrons in the half-filled f shell and is mediated via RKKY interaction by the conduction electrons. Close to the Fermi energy EF an exchange-split d-like surface state is found, which is thought to be responsible for peculiar magnetic effects of the Gd(0001) surface. The behaviour of this surface state close to Curie temperature TC has been controversially discussed: spin-resolved inverse photoemission (IPE) has identified a surface state with both, minority and majority components right above the Fermi energy EF already 10 years ago.1 While the majority state shifts to higher energies upon approaching TC the minority state shifts to lower energies. This Stoner-like collapsing band behaviour is in contradiction to results from spin-resolved photoemission (PE), where the surface state shows up at 0.2 eV below EF and exhibits spin-mixing behaviour upon approaching TC.2 The present widely accepted picture of the surface state on Gd(0001) comprises a majority component 0.2 eV below EF and a minority component 0.4 eV above EF at low T. As identified by spin-integrated scanning tunneling spectroscopy3 the exchange splitting slightly reduces with increasing T and remains 0.4 eV at TC.3 However, the unoccupied majority component as identified by IPE still remains mysterious. One reason for the conflicting results might be found in different sample conditions since the Gd films are usually grown on W(110), a material with considerably different lattice constant than Gd. To overcome this suspicion, we performed combined spin-resolved PE and IPE measurements on one and the same sample preparation of a 30 ML Gd film grown on Y(0001). We were able to identify two surface states with their minority and majority components well separated from EF. While the occupied surface state shows spin-mixing behaviour as observed in other PE experiments, the unoccupied surface state exhibits an exchange splitting of 250 meV that vanishes at TC.

1Donath et al., PRL 77, 5138 (1996).
2Li et al., Phys. Rev. B 51, 13895 (1995).
3Getzlaff et al., JMMM 184, 155 (1998).