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Soft x-ray magnetic circular dichroism (XMCD) spectra have been investigated for different crystallographic projections of CrO 2 . Strong anisotropic orbital Cr 3d contributions and a change of sign of the XMCD signal is observed and attributed to t 2g majority states near the Fermi level. Additionally, moment analysis exhibits anisotropic behavior in the projected spin contributions of CrO 2 assigned to a strong magnetic dipole term T z , consistent with an intrinsic magnetic easy axis behavior along the CrO 2 [001] axis. A reduced projected isotropic Cr 3d spin moment has been interpreted in terms of hybridization with oxygen. PACS numbers: 75.30.Gw, 78.70.Dm, 87.64.Ni In the past few years, CrO 2 has attracted revived interest due to its remarkably high spin polarization at the Fermi energy, theoretically predicted to be 100% [1][2][3][4] and recently verified by superconducting tunneling spectroscopy at T 18 K [5,6] and spin-polarized photoemission spectroscopy at T 293 K [7]. The reason for this revival is mainly related to promising future applications such as magnetic tunneling and spin injection devices on the basis of CrO 2 electrodes [8]. The oxygen mediated coupling and its half metallic nature are a challenging problem for theoretical investigations, originated by the presence of oxygen hybridization, double exchange, self-doping, and correlation effects [2]. The quantitative influence of orbital moments [9], inner 3d shell spin-orbit coupling, and the magnetic dipole term T z [10] All spectra were recorded in total electron yield mode at the bending-magnet beam line PM I at BESSY II with an energy resolution E͞DE 2000 in an applied magnetic field of 65 kOe (flipped at each data point). The degree of circular polarization was 95%. All spectra have been measured at 80 K. Spectra are carefully background subtracted and edge normalized using the same background and normalization factor for parallel and antiparallel orientation of the photon beam k vector with respect to the sample magnetization. Further details of the experimental setup and data analysis have been published elsewhere [19]. The experimental geometry is schematically shown in the inset of Fig. 1a. X-ray magnetic circular dichroism (XMCD) spectra were taken at fixed grazing incidence (f 60 ± ) and the sample was rotated by the angle q around the surface normal. Figure 1a shows normalized XAS spectra for q 7 ± and Fig. 1b shows the corresponding XMCD signals for nearly a axis (7 ± ), c axis (86 ± ) and intermediate (40 ± ) projected azimuthal sample orientations. Compared to other 3d metal XMCD spectra [20][21][22], very strong and pronounced changes as a function of the azimuthal angle q are present. For c-axis enhanced projection (q 86 ± ) a direct observable change of sign at 587 eV is present. The negative XMCD intensity suggests a strong increase of the projected orbital moment for increased c-axis projections. In contrast only very small changes in the averaged Cr L 2,3 XAS are present and therefore not shown. We have measured q a...

Highly a-axis-textured CrO 2 films have been deposited on Al 2 O 3 (0001) and on isostructural TiO 2 (100) substrates by a chemical vapour deposition technique. For Al 2 O 3 substrates a columnar growth of CrO 2 (010) on an initial Cr 2 O 3 (0001) layer has been found in transmission electron microscopy as well as in x-ray diffraction investigations. The sixfold in-plane symmetry of a (0001)-oriented Cr 2 O 3 initial layer leads to three equivalent in-plane orientations of the CrO 2 unit cell as confirmed by electron diffraction and scanning electron microscopy. The growth can be understood by a simple model of the in-plane symmetries of the Al 2 O 3 (0001), Cr 2 O 3 (0001), and CrO 2 (010) lattices. The growth on TiO 2 (100) substrates leads to (100)-oriented CrO 2 films of higher crystalline quality than the ones grown on Al 2 O 3 (0001). Transmission electron microscope images show growth of CrO 2 (100) directly on the TiO 2 (100) substrates and no significant Cr 2 O 3 inclusions within the CrO 2 (100) layer. All contributions to the magnetoresistance (MR) due to anisotropic MR, Lorentz MR, spin disorder, and intergrain tunnelling MR have been determined and partly correlated with the crystalline properties of the samples investigated. For films of both types the intrinsic linear contribution to the high-field MR does not depend on the crystalline quality of the films and supports the suggested intrinsic doubleexchange mechanism for CrO 2 .