Structure, reactivity, electronic configuration and magnetism of samarium atomic layers deposited on Si(001) by molecular beam epitaxy

• Published in: Applied surface science 2013-02, Vol.267, p.106-111
• Main Authors: Gheorghe, Nicoleta G., Lungu, George A., Husanu, Marius A., Costescu, Ruxandra M., Macovei, Dan, Teodorescu, Cristian M.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; LEED; MBE; MOKE; Physics; Samarium; Samarium silicide; X-ray absorption; XPS
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2012.08.016

► Sm deposited on Si(001) at temperatures below 400°C is ferromagnetic. ► Sm/Si(001) forms a mixture of Sm metal, Sm4Si3 and SmSi2. The first two phases are ferromagnetic. ► The Sm magnetic moment in the ferromagnetic phases (about 2.3Bohr magnetons) exceeds its value for bulk Sm (1.7Bohr magnetons). The surface structure, interface reactivity, electron configuration and magnetic properties of Sm layers deposited on Si(001) at various temperatures are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and magneto-optical Kerr effect (MOKE). It is found that metal Sm is present on samples prepared at low temperature, with an interface layer containing SmSi2 and Sm4Si3. When samples are prepared at high temperature, much less metal Sm is found, with an increasing amount of SmSi2. Room temperature ferromagnetism is observed for all prepared layers, with a decrease of the saturation magnetization when samples are prepared at high temperature. It is found that ferromagnetism implies mostly a compound with approximate stoichiometry Sm4Si3. Also, the decrease in the intensity of the XAS 2p3/2→3d white lines with the corresponding increasing amount of SmSi2 may be explained by assuming a higher occupancy of Sm 5d orbitals (5d2 configuration), most probably due to hybridation effects.