Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 68: Transport: Spintronics, Magnetotransport 2 (jointly with HL and MA)
TT 68.1: Talk
Friday, March 15, 2013, 09:30–09:45, H20
Bulk sensitive photoelectron spectroscopy on CrO2 thin films — •Jonas Weinen1, Stefano Agrestini1, Martin Rotter1, Simone G. Altendorf1, Zhiwei Hu1, Chun-Fu Chang1, Arun Gupta2, Yen Fa Liao3, Ku-Ding Tsuei3, and Liu Hao Tjeng1 — 1Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden — 2The University of Alabama, Tuscaloosa, USA — 3National Synchrotron Radiation Research Centre, Hsinchu, Taiwan
For transition metal compounds with a high oxidation state the so-called charge transfer energy can become negative, with the result that a spontaneous electron redistribution could occur in which oxygen holes are formed. Such seems to be the case for the ferromagnet CrO2. Using the LDA+U method, Korotin et al. [PRL 80, 4305 (1998)] calculated that the material is a metal and remains a metal even for very large values of U. This suggests that it is not so much the Cr 3d states that determine whether the system is metallic or insulating, but rather that it is the O 2p states which straddle the chemical potential.—Several photoelectron spectroscopy (PES) studies have been reported in the literature, but the results are not consistent, supposedly related to the fact that the surface of CrO2 tends to decompose to Cr2O3 under vacuum conditions, so that surface sensitive PES may not have probed the true bulk spectrum of CrO2.—We set out to perform bulk sensitive photoemission experiments below and above TC on CrO2 thin films using our HAXPES system at SPring-8. Our results suggest that CrO2 may be considered more like a bad metal rather than a normal metal.
This work is also supported by DFG through FOR1346.