Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 31: Surface Magnetism / Magnetic Imaging II

MA 31.7: Talk

Thursday, March 25, 2010, 16:45–17:00, H23

Influence of Co-Cu alloying on spin-dependent surface states — •Tobias Allmers¹, Markus Donath¹, Jürgen Braun², Jan Minár², and Hubert Ebert² — ¹Physikalisches Institut, University of Münster, Germany — ²Dep. Chemie und Biochemie, LMU Universität München, Germany

In literature it is reported that Co films grown on Cu(001) held at 300 K can be annealed to ≈500 K without Co diffusion towards the surface [1]. As will be shown in this contribution, Cu diffusion takes place even at 295 K. This can be avoided when the film is grown at 115 K. In this case the surface can be annealed to 555 K without Cu diffusion. For annealing temperatures above 555 K an alloying between Co and Cu takes place. Due to the low miscibility of Co and Cu the alloy consists of different phases, mainly Co- and Cu-rich areas. The alloying has a significant influence on the surface states. It results in a suppression of the occupied minority surface state around Γ [2]. This indicates that the symmetry cap closes for the Co-Cu alloy due to the non-magnetic Cu. In contrast, the projected bulk band structures for Co(001) and Cu(001) are very similar to each other including the gap position. Consequently, the unoccupied surface state X persists for the Co-Cu alloy. The spin splitting is reduced with increasing Cu content. The same is true for the exchange splitting of the image potential state. Our results show impressively how important a careful thin film preparation is for the study of pure Co films. [1] Schneider et al., in Magnetism and Structure in Systems of Reduced Dimension, p. 453 (Plenum Press, 1993). [2] Schmidt et al., J. Phys. D 41 (2008) 164003.