Year: 2019
Type: article
Abstract: We investigated the electronic structure of a delafossite oxide CuAlO$_2$ in comparison with CuCrO$_2$, using vacuum ultraviolet (VUV) and hard x-ray (HX) photoemission spectroscopy (PES) and band structure calculations within the local-density approximation +$U$ scheme. Cu 3$p\! -\! 3d$ resonant PES and Cu $2p$ core-level HX-PES give concrete evidence that the Cu valence in CuAlO$_2$ is monovalent, which makes a sharp contrast to CuCrO$_2$ that showed contradictory results depending upon probing methods [Yokobori \textit{et al.}, Phys. Rev. B \textbf{87}, 195124 (2013)]. We further noticed weak but detectable satellite structures due to Cu$^{2+}$ state in the Cu $2p$ HX-PES spectrum of CuCrO$_2$, surprisingly, without an observable main peak due to the Cu$^{2+}$ state. Comparisons between the valence-band HX-PES spectra and the band structure calculations revealed a significant amount of the Cu $4s$ and Al $3s$/Cr $4s$ states in the valence band. The above results can reasonably be explained by the Cu $3d, 4s-$Cr $3d$ charge transfer model that we previously proposed in the above paper, thereby demonstrating the critical role of empty $3d$ orbitals in the electronic structure of the copper delafossite oxides.
Institutions: Tokyo University of Science, Kagoshima University, Japan Synchrotron Radiation Research Institute, Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya University, High Energy Accelerator Research Organization, Photon Factory, Center for Spintronics Research Network, Osaka University
Language: English
Subfield: Surfaces, Coatings and Films
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Awards: Seeking for the electronic-structure origin of the unusual spin states in trivalent Co oxides, Research for large thermoelectric responses of transition metal oxides by controlling nanostructure, 軌道/電荷の揺らぎを用いた低熱伝導性-高電気伝導性素子の開発, Study of Variable Emitatnce Device for Spacecraft, First-Principles-Calculation Program of Valence-Band Photoemission Spectrum by an Atomic-Limit Model on the basis of FLAPW Method, Search for a systematic electronic structure in oxides with two transition metals, Multi-probe study on the spin and orbital quantum critical point in cobaltites, G8744134649, Search for novel physical properties in spin-orbit fluctuated systems
OpenAlex ID: W2951973102