2004/09/24 by A. Talapatra, S. K. Bandyopadhyay, Talapatra, A. +10
Physics and Astronomy · #FOS: Physical sciences #Superconductivity (cond-mat.supr-con) #Superconductivity in MgB2 and Alloys #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.cond-mat/0409654
14 pages, 7 figures
arxiv created 2004/09/24 · openalex publication_date 2004/09/24 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Core level X-ray Photoelectron Spectroscopy (XPS) studies have been carried out on polycrystalline MgB2 pellets over the whole binding energy range with a view to having an idea of the charge state of Magnesium (Mg). We observe 3 distinct peaks in Mg 2p spectra at 49.3 eV (trace), 51.3 eV (major) and 54.0 eV (trace), corresponding to metallic Mg, MgB2 and MgCO3 or, divalent Mg species respectively. Similar trend has been noticed in Mg 2s spectra. The binding energy of Mg in MgB2 is lower than that corresponding to Mg(2+), indicative of the fact that the charge state of Mg in MgB2 is less than (2+). Lowering of the formal charge of Mg promotes the sigma to pi electron transfer in Boron (B) giving rise to holes on the top of the sigma-band which are involved in coupling with B E2g phonons for superconductivity. Through this charge transfer, Mg plays a positive role in hole superconductivity. B 1s spectra consist of 3 peaks corresponding to MgB2, boron and B2O3. There is also evidence of MgO due to surface oxidation as seen from O 1s spectra.