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A.N.Andriotis andriot@iesl.forth.gr esperia.iesl.forth.gr/~andriot

A.N.Andriotis andriot@iesl.forth.gr http://esperia.iesl.forth.gr/~andriot. Theoretical Condensed Matter Physics and Materials Research Heraklion, 28 March 2006. Theoretical Condensed Matter Physics and Materials Research. Clusters. Materials of current and intense technological

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A.N.Andriotis andriot@iesl.forth.gr esperia.iesl.forth.gr/~andriot

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  1. A.N.Andriotisandriot@iesl.forth.grhttp://esperia.iesl.forth.gr/~andriotA.N.Andriotisandriot@iesl.forth.grhttp://esperia.iesl.forth.gr/~andriot Theoretical Condensed Matter Physics and Materials Research Heraklion, 28 March 2006

  2. Theoretical Condensed Matter Physics and Materials Research Clusters • Materials of current and • intense technological • and basic research • interest. • Applications (indicatively): • - New (magnetic) materials • - Sensors • Nano-electronics • Energy (Hydrogen) storage • Catalysis • Medical applications Fullerenes New and Smart Materials Dilute Magnetic Semicond. Nanotubes Nanowires

  3. Theoretical Condensed Matter Physics and Materials Research ACTIVITIES Clusters Grain Magnetic Materials for Advanced Magnetic Storage Devices Fullerenes s-p Magnetism in Carbon-based Materials New and Smart Materials Dilute Magnetic Semicond. Magnetism in non-traditional Inorganic Materials Nano-electronics Nanotubes Nanowires

  4. Grain Magnetic Materials for Advanced Magnetic Storage Devices; (grains of diameter 2-10nm) Co-Pt clusters (2 nm) (Lyon) • Enhancing the magnetism of transition metal grains (Our contribution : Structural- and T-effects on electronic and magnetic properties) • Fe-Co grains break the Super-para-magnetic limit • ‘AMMARE’-GROWTH PROJECT(Coordinated by IESL ; terminatedsuccessfully 31st Dec. 2004; budget 2,322,800 Euros; 73.17 % EU-funding) Co clusters on Au(111) (STM) (Strasbourg)

  5. Grain Magnetic Materials Conclusion : Binary grains (2-10 nm in diameter) made of 3d-Transition Metals can enhance their magnetic moments by exploiting effects of magnetic anisotropy and rehybridization processes; template assistance may help to this direction. • A.N.Andriotis et al, PRL 93, 026402 (2004); JCP 120, 11901 (2004); JCP 119, 7498 (2003), PR B68, 125407 (2003); PR B72, 104417 (2005)

  6. Transition-Metal ClustersT=0 and collinear approximation Fe-Co clusters : Magnetic Enhancement Magnetic Moments of Ni-clusters Co induces structural changes to Fe Clusters. These lead to rehybridization of MOs and re-determination of d-band filling. From : M.B.Knickelbeim, JCP, 116, 9703 (2002)

  7. Transition-Metal ClustersNon-zero-T and non-collinear approximation CURRENT WORK Ni43 and Ni201 T=400 500 600 K T

  8. Theoretical Condensed Matter Physics and Materials Research Clusters Grain Magnetic Materials for Advanced Magnetic Storage Devices Fullerenes s-p Magnetism in Carbon-based Materials New and Smart Materials Dilute Magnetic Semicond. Magnetism in non-traditional Inorganic Materials Nano-electronics Nanotubes Nanowires

  9. s-p type ferromagnetismin C-based materialsA.N.Andriotis et al, PRL 90, 026801 (03) • 2D-Rh-C60-polymer • The defect model appears as a generic model for magnetism in systems with only s-p electrons

  10. Interplay between Nitrogen impurities and vacancies in C60s Spin density Charge density

  11. Interplay between Nitrogen impurities and vacancies in SWCNs Spin-density Charge density

  12. Theoretical Condensed Matter Physics and Materials Research Clusters Grain Magnetic Materials for Advanced Magnetic Storage Devices Fullerenes s-p Magnetism in Carbon-based Materials New and Smart Materials Dilute Magnetic Semicond. Magnetism in non-traditional Inorganic Materials Nano-electronics Nanotubes Nanowires

  13. The defect model appears as a generic model for magnetism in non-traditional inorganic materials NEW CLASS of magnetic Materials FUTURE WORK : Exploit this new magnetism for fabricating new materials Zn(TM)O Ti (TM) O2 Ca(Vac)O Hexaborides Dilute magnetic semiconductors s-p type ferromagnetismin non-traditional inorganic materialsA.N.Andriotis et al, Condens.Matter 17, L35 (05)

  14. s-p type ferromagnetismin non-traditional inorganic materialsA.N.Andriotis et al, Condens.Matter 17, L35 (05),PRL 87, 066802 (01) • Generalized McConnell model : Vacancies behave as donors while the 2+2 cycloaddition bonds behave as acceptors • 500 downloads during 2005 (Editor’s aknowledgment)

  15. Theoretical Condensed Matter Physics and Materials Research Clusters Grain Magnetic Materials for Advanced Magnetic Storage Devices Fullerenes s-p Magnetism in Carbon-based Materials New and Smart Materials Dilute Magnetic Semicond. Magnetism in non-traditional Inorganic Materials Nano-electronics Nanotubes Nanowires

  16. Nanotubes (NTs) • Structural and electronic properties of NTs (Carbon-, Si-,SiC-, BN-based) Future applications in NTs made of other materials (e.g., SiO2, VO2 ) for spintronics applications • Transport properties of NTs • Functionalized NTs • Hydrogen storage (FUTURE)

  17. Nano-electronics PRL cover-page Issue : Vol. 87, No.6 6 Aug. 2001

  18. Nano-electronics Major achievements (predictions) • Rectification and switching properties of branched Carbon Nanotubes • Stability of Si-nanotubes by encapulation of transition metals • A.N.Andriotis et al, PRL 87, 066802 (2001); PR B65, 165416 (2002); PRL 91, 145501 (2003); PR B69, 115322 (2004).

  19. Nano-electronics SWCN in contact with metal leads Si-NT stabilized by a Ni-chain Branched SWCNs I-V curves for branched SWCNs

  20. Y-SWCN : Ballistic SwitchingBandaru et al Nature Materials 4, 663 (2205)Andriotis and Menon (2006)

  21. Si-nanowires(submitted 2005) Transition from Direct to Indirect Gap at 4.5-5.3 nm Tetrahedral grown Along <111> direction; D=1-5 nm tetrahedral fcc-34 sc-46 polycrystalline

  22. Methods employed • Orthogonal and Non-orthogonal TBMD - M.Menon and K.R.Subbaswamy, PRB 50, 11577 (1994) - A.N.Andriotis and M.Menon PRB 57, 10069 (1998) • Surface Green’s Function Matching (SGFM) method - S.Datta in “Electronic Transport in Mesoscopic Systems”, (1995) - A.N.Andriotis and M.Menon, JCP 115, 2737 (2001) • Transfer Hamiltonian Approach (THA) method - J. Bardeen, PRL, 6, 57 (1961) - A.N.Andriotis, M.Menon and D.Srivastava, JCP 117, 2836 (2002) • Ab initio methods (Gaussian 98)

  23. Publications 2000-2005

  24. Collaborators • Prof. Madhu Menon(Univ. of Kentucky, Lexington, KY) • Dr. R. Michael Sheetz(Univ. of Kentucky, Lexington, KY) • Prof. Leonid Chernozatonskii(Institute of Biochemical Physics, Russian Academy of Sciences, Moscow) • Dr. Deepak Srivastava, NASA Ames, USA • Dr. Inna Ponomareva, Russian Academy of Sciences, Moscow, Russian Federation • Dr. G. Froudakis, Chemistry Dpt., Univ. of Crete • Mr. G. Mpourmpakis, Chemistry Dpt., Univ. of Crete • Mr. Z. Fthenakis, IESL, FORTH, Crete

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