The apparent Gd 4f binding energy in photoemission spectroscopy is strongly affected by both correlation energy contributions, and final state effects in photoemission. The latter are clearly strongly influenced by metallicity and screening [1]. To understand these various contributions to the observed electronic structure of gadolinium compounds, we compare a series of studies on gadolinium compounds and clusters with pure and alloyed gadolinium films [2]. These materials range from the metallofullerenes, in which a metal atom or cluster is encapsulated inside a fullerene, such as in the “buckyball” C60, to more conventional rare earth compounds like GdN, Gd2O3, Gd doped HfO2 and Gd-Ni alloys. The Gd3+ ion exhibits bonding and hybridization that is quite different for these various compounds. While the total spin multiplicity of Gd is maximum because of its half-filled 4f state, and the atomic orbitals are strongly hybridized with the C60 molecules in the example of Gd@C60 [3] or oxygen in the case of Gd doped HfO2 [4], while the highest possible symmetry site for gadolinium is generally not favored. These results are to some extent a confirmation of theoretical expectations but there are complications. There is experimental evidence for intra-atomic hybridization with both the unoccupied and occupied Gd 4f states, as well as band dispersion even for the occupied Gd 4f states in some systems [2] and spin dependent screening [5].

 

[1] J.E. Ortega, F.J. Himpsel, Dongqi Li and P.A. Dowben, Solid State Commun. 91 (1994) 807-811

[2] T. Komesu, H. K. Jeong, David Wooten, Ya. B. Losovyj, J. N. Crain, M. Bissen, F. J. Himpsel, J. Petrosky, Jinke Tang, Wendong Wang, I.N. Yakovkin, and P. A. Dowben, Physica Status Solidi B 246 (2009) 975-980

[3] R. F. Sabirianov, W. N. Mei, Jing Lu, Y. Gao, X. C. Zeng, R.D. Bolskar, P. Jeppson, Ning Wu, A.N. Caruso, and P. A. Dowben, J. Phys. Cond. Matter 19 (2007) 082201

[4] Ya. B. Losovyj, I. Ketsman, A. Sokolov, K. D. Belashchenko, P.A. Dowben, J. Tang, Z. Wang, Appl. Phys. Lett. 91 (2007) 132908

[5] Hae-Kyung Jeong, R. Skomski, D. Wisbey, P.A. Dowben, Physics Letters A 341 (2005) 508-515

This work has been undertaken with Y. Losovyj, T. Komesu, Hae-Kyung Jenong, I. Ketsman, N. Wu, A. Sokolov, J. Colon Santana, W. Choe, K. D. Belashchenko, R. F. Sabirianov, W. N. Mei, Jinke Tang, A.N. Caruso, D. Wooten, R. Skomski, F. Himpsel, E. Vescovo