a.n.andriotis andriot@iesl.forth.gr andriot andriot@iesl.forth.gr theoretical condensed matter...

A.N.Andriotisandriot@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

New and SmartMaterials

Clusters

NanotubesNanowires

DiluteMagnetic Semicond.

Fullerenes

Materials of current and intense technological and basic research interest.

Applications (indicatively):- New (magnetic) materials- Sensors- Nano-electronics- Energy (Hydrogen) storage- Catalysis - Medical applications

Theoretical Condensed Matter Physics and Materials Research

New and SmartMaterials

Clusters

NanotubesNanowires

DiluteMagnetic Semicond.

Fullerenes

Grain Magnetic Materials for Advanced Magnetic

Storage Devices

s-p Magnetismin Carbon-based Materials

Magnetism in non-traditionalInorganic Materials

Nano-electronics

ACTIVITIES

Grain Magnetic Materials for Advanced Magnetic Storage Devices; (grains of diameter 2-10nm)

• 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 ; terminated successfully 31st Dec. 2004; budget 2,322,800 Euros; 73.17 % EU-funding)

Co-Pt clusters (2 nm) (Lyon)

Co clusters on Au(111) (STM) (Strasbourg)

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)

Transition-Metal ClustersT=0 and collinear approximation

Magnetic Moments of Ni-clustersFe-Co clusters : Magnetic Enhancement

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)

Transition-Metal ClustersNon-zero-T and non-collinear approximation

CURRENT WORK

TT=400 500 600 K

Ni43 and Ni201

Theoretical Condensed Matter Physics and Materials Research

New and SmartMaterials

Clusters

NanotubesNanowires

DiluteMagnetic Semicond.

Fullerenes

Grain Magnetic Materials for Advanced Magnetic

Storage Devices

s-p Magnetismin Carbon-based Materials

Magnetism in non-traditionalInorganic Materials

Nano-electronics

s-p type ferromagnetism in C-based materials A.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

Interplay between Nitrogen impurities and vacancies in C60s

Spin density Charge density

Interplay between Nitrogen impurities and vacancies in SWCNs

Spin-density Charge density

Theoretical Condensed Matter Physics and Materials Research

New and SmartMaterials

Clusters

NanotubesNanowires

DiluteMagnetic Semicond.

Fullerenes

Grain Magnetic Materials for Advanced Magnetic

Storage Devices

s-p Magnetismin Carbon-based Materials

Magnetism in non-traditionalInorganic Materials

Nano-electronics

s-p type ferromagnetism in non-traditional inorganic materials

A.N.Andriotis et al, Condens.Matter 17, L35 (05)

• 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 ferromagnetism in non-traditional inorganic materials

A.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)

Theoretical Condensed Matter Physics and Materials Research

New and SmartMaterials

Clusters

NanotubesNanowires

DiluteMagnetic Semicond.

Fullerenes

Grain Magnetic Materials for Advanced Magnetic

Storage Devices

s-p Magnetismin Carbon-based Materials

Magnetism in non-traditionalInorganic Materials

Nano-electronics

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)

Nano-electronics

PRL cover-pageIssue : Vol. 87, No.66 Aug. 2001

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).

Nano-electronicsSWCN in contact with metal leads Si-NT stabilized by a Ni-chain

Branched SWCNs I-V curves for branched SWCNs

Y-SWCN : Ballistic SwitchingBandaru et al Nature Materials 4, 663 (2205)

Andriotis and Menon (2006)

Y-SWCN : Ballistic SwitchingBandaru et al Nature Materials 4, 663 (2205)

Andriotis and Menon (2006)

Si-nanowires(submitted 2005) Transition from Direct to

Indirect Gap at 4.5-5.3 nm

tetrahedral

fcc-34

sc-46

polycrystalline

Tetrahedral grown Along <111> direction; D=1-5 nm

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)

Publications 2000-2005JOURNAL 2000 2001 2002 2003 2004 2005 Total

PRL 1 1 2 1 1 6PRB 2 2 1 2 2 2 11

NanoL 1 1 2APL 1 1 1 1 4

CPL 1 1 2

JCP 1 1 2 1 5

JPCM 1 1

NJP 1 1 2

EPL

Other 1

1

1

1

2

Total 5 6 4 9 5 7 36

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