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Multifunctional molecular materials E. Coronado

Multifunctional molecular materials E. Coronado. Instituto de Ciencia Molecular. Molecule A Property A. Molecule B Property B. Hybrid Molecular Material A m B n. Coexistence Sinergy Exclusion. Hybrid Approach to Multifuncional Materials. The hybrid approach. cation-anion

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Multifunctional molecular materials E. Coronado

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  1. Multifunctional molecular materialsE. Coronado Instituto de Ciencia Molecular

  2. Molecule A Property A Molecule B Property B Hybrid Molecular Material AmBn Coexistence Sinergy Exclusion Hybrid Approach to Multifuncional Materials

  3. The hybrid approach cation-anion host-guest B A

  4. The hybrid approach To 1D chains B A

  5. The hybrid approach To multilayers cation-anion host-guest A B

  6. DUAL-FUNCTION MATERIALS Properties: ferromagnetism / electric conductivity / chirality FERROMAGNETIC CONDUCTORS Ferromagnetic layer + conductive molecular layer  CHIRAL CONDUCTORS Chiral molecule + conductive molecular layer  CHIRAL MAGNETS Chiral molecule + Ferromagnetic lattice

  7. SWITCHING MATERIALS SWITCHING MAGNETS Switching molecule + ferromagnetic lattice SWITCHING CONDUCTORS Switching molecule + conductive molecular layer

  8. Outline Dual-function materials II. Switching materials

  9. Outline Dual-function materials Ferromagnetic conductors Chiral conductors II. Switching materials

  10. HISTORY 70’s Molecular metals 80’s Molecular superconductors Molecular magnets 90’s Paramagnetic conductors Paramagnetic superconductors Antiferromagnetic superconductors 00’s Ferromagnetic conductors Single component molecular conductors (A. Kobayashi) Single component magnetic conductors (R.Llusar)

  11. M. Kurmoo, P. Day et al. J. Am. Chem. Soc. 1995, 117, 12209 [BEDT-TTF]4[(H3O)Fe(ox)3].C6H5CN A Paramagnetic superconductor (Tc = 7 K) H.Kobayashi BETS: FeX4 salts

  12. Ferromagnetic conductors [BEDT-TTF]3[MnCr(ox)3].CH2Cl2 E. Coronado et al. Nature, 2000, 408, 447-449

  13. [BEDT-TTF]3[MnCr(ox)3].CH2Cl2 Magnetic properties Soft ferromagnet Tc = 5.5 K

  14. s q sII = 104 sI [BEDT-TTF]3[MnCr(ox)3].CH2Cl2 Electric properties sRT = 250 S.cm-1

  15. H q [BEDT-TTF]3[MnCr(ox)3].CH2Cl2 Magnetoresistance P. Goddard, V. Laukhin and A.K. Klehe

  16. Ferromagnetic conductors [D]x[MIICr(ox)3].CH2Cl2 BEDT ≈3 Mn(ferro) 5.5 250 (metal) BEST ≈2 Mn(ferro) 5.6 10-6 (insulator) BETS ≈3 Mn(ferro) 5.2 1 (metal/semi) BET ≈3 Mn(ferro) 5.6 4 (metal/semi) [D]x[MIIRh(ox)3].CH2Cl2 D x MII Tc(K) sRT (S.cm-1) BEDT 2.53 Mn(para) - 13 (metal/semi) 2 < x < 3 D x MII Tc(K) sRT (S.cm-1) BEDT ≈3 Co(ferro) 9.2 1 (metal/semi) BEST ≈2 Co(ferro) 10.8 10-6 (insulator) BET ≈3 Co(ferro) 13.0 21 (metal/semi) Coronado, Galan et al., J. Am. Chem. Soc.2003, 125, 10774; Synth. Met.2003, 135-136, 687. Inorg. Chem.2004, 43, 4808.

  17. Can the electric properties be improved? Structural disorder in the ethylenic groups

  18. Solution: Use a chiral TTF derivative chiral tetra(methyl)-BEDT-TTF Prof. John Wallis Nottingham Trent Univ. (UK) TM-ET Consequence: A new class of multifunctional material electric + magnetic + chiral (chiral magnetic conductor)

  19. Strategies to chiral molecular conductors i) Inorganic chiral complex + non chiral organic donor BEDT-TTF tartrate complexes E. Coronado, J. R. Galan et al. Inorg. Chem. 2004, 43, 8072 [Sb2(L-tar)2]2- ii) Inorganic non chiral complex + chiral organic donor

  20. CHIRAL CONDUCTORS INTEREST Electrical Magnetochiral anisotropy Rikken et al. Phys. Rev. Lett. 2001, 87, 236602 Anisotropy in the electrical magnetoresistance DR = R(I, H) - R(-I, H) ≠ 0 Interesting in spintronics DR = R(I, H) - R(I, -H) ≠ 0

  21. b-[TM-ET]x[MnCr(ox)3].CH2Cl2; x ≈ 2.7 Transport properties. In layer resistivity

  22. High field measurements at NHMFL Los Alamos and Tallahassee (J. Singleton) Interlayer resistance ( zz). • Negative MR at low fields; • Shubnikov-de Haas oscillations (more than one series); • But.... very large value of resistance => sample looks insulating; • Behaviour resembles that of the ”-(ET)4X salts with oxalate anions (see Coldea, this conference and Phys. Rev. B 04, 05) We now use the Shubnikov-de Haas oscillations to extract information about the Fermi surface.

  23. Stronger series of oscillations: subtract background MR Shubnikov de Haas oscillations are clearly visible in the oscillatory component of the magnetoresistance at T = 550 mK. Their inverse field positions (right hand plot) give the frequency (i.e. cross-sectional area) of the Fermi surface. The oscillations have a frequency of 215 T, corresponding to a cross-sectional area of a few percent of the Brillouin zone. Again, this is very similar to the behaviour of the ” (BEDT-TTF) salts (see Coldea et al., Phys. Rev. B (2005)).

  24. Tilting the sample so that the field is no longer perpendicular to the conducting planes shows a second, lower, frequency more clearly These oscillations are probably suppressed by a “spin zero” close to  = 0. Once again, we can plot the oscillation inverse fields and find the frequency, i.e. Fermi surface cross-section. • This material appears to possess two quasi-two-dimensional Fermi-surface pockets, with areas corresponding to frequencies of 31 T and 215 T (c.f. Coldea et al., Phys. Rev. B 2004, 2005 and this conference).

  25. Temperature dependence of the magnetoresistance Interlayer magnetoresistance is strongly temperature dependent, and the absolute value of the resistivity is large. On the other hand, there are metallic quasiparticles present (Shubnikov-de Haas oscillations). This suggests that the samples undergo phase separation into metallic and insulating regions (a very widely found phenomenon in low -quasiparticle density organics manganites etc.). The temperature dependence of the Shubnikov-de Haas oscillations gives the quasiparticle effective mass for the larger of the two Fermi-surface pockets as 2.0 me.

  26. Field dependence of the resistivity At low fields, the Mn-containing compounds show negative magnetoresistance, possibly associated with spin-disorder scattering. This vanishes at high T. Sadly, no evidence for magnetochiral anisotropy was observed (any apparent asymmetry is due to T fluctuations), perhaps because the interlayer transport is incoherent.

  27. Field dependence of the resistivity None of the materials showed definite magnetochiral anisotropy at any temperature (0.5-100 K); any apparent asymmetry is due to T variations. This is perhaps because the interlayer transport is incoherent in these materials, as evidenced by the very large interlayer resistances.

  28. Outline Dual-function materials Magnetic Molecular Conductors Chiral Conductors II. Switching materials

  29. Outline Dual-function materials Magnetic Molecular Conductors Chiral Conductors II. Switching materials Molecular-based Piezomagnets

  30. SWITCHING MATERIALS ONE NETWORK TWO NETWORK

  31. Cr a = b = c =10.6720(2) a = b = g =90.00 C N Fe SWITCHING MAGNETS Molecular switch + Magnetic lattice Piezomagnetic materials 250 mm Soft ferromagnet (Tc = 19 K) K0.4FeII4[CrIII(CN)6]2.8 ‘1.2·16H2O K0.4FeII4[CrIII(CN)6]2.8·16H2O Single crystals of a Prussian blue derivative

  32. K0.4FeII4[CrIII(CN)6]2.8·16H2O c M Magnetic measurements under pressure

  33. + D P - D P CrIII FeII N FeII N C C CrIII K0.4FeII4[CrIII(CN)6]2.8 ‘1.2·16H2O S=0 S=2 Piezo-switching of the magnetic interaction via a CN rotation CoII-FeIII Photoswitching (Hashimoto, Ohkoshi) Piezoswitching (V. Ksenofontov) via electron transfer

  34. M K0.4FeII4[CrIII(CN)6]2.8 ‘1.2·16H2O Reversibility of the process

  35. MII-CN 2105 cm-1 MIII-CN 2157 cm-1 RAMAN SPECTROSCOPY UNDER PRESSURE Valentín García Baonza (Universisdad Complutense de Madrid) P = 15 kbar P = 0 kbar E.Coronado, F. M. Romero et al. J. Am. Chem. Soc. 2005 (DOI: 10.1021/ja043166z)

  36. Conclusion • Multifunctional molecular materials : Complex, beautiful and useful chemical objects / New and attractive physical objects We have reported here the first multifunctional material: A chiral ferromagnetic conductor • Few examples of dual-function or switching materials have been discovered so far • The hybrid approach has shown to be very useful to create these kinds of unconventional materials • Not only crystals are interesting. Hybrid thin films and nanothings are also searched

  37. JR Galán-Mascarós FM. Romero CJ Gómez A Murcia A Forment MC Giménez H. Bolink Grupo de Materiales Moleculares

  38. Financial support • European Union: • Spanish Ministry of Education and Science • Generalitat Valenciana

  39. Molecular magnetic semiconductors: Hybrid thin films of single-molecule magnets in organic semiconductors

  40. 8 Mn(III) S =2 4 Mn(IV) S =3/2 Single molecule magnets [Mn12O12(O2CR3)16(H2O)4] Molecular magnetic memory Quantum tunnelling effects S = 10

  41. Single-molecule nanomagnets. Energy barrier MS= 0 DS2 MS= 10 MS= -10 [Mn12O12(O2CMe)16(H2O)4], “Mn12” Ground spin state S = 10 The energy barrier increases with the ground spin state, S, and with its (negative) magnetic anisotropy, D.

  42. Thin films of Mn12 embedded in organic semiconductors Mn12 as electron acceptor [Mn12O12(O2CPhF5)16(H2O)4] TPD H. Bolink et al. Adv. Mater,2005, 17, 1018

  43. Magnetic molecular semiconductors TPD: Mn12 Chemical doping: oxidation of TPD with Mn12 . + + Mn12 + Mn122- SbF6- RT  10-12 - 10-9 S/cm RT  10-9 - 1 S/cm

  44. Conductivity vs doping with Mn12

  45. Useful as hole injection layer in Organic Light Emitting Diodes + - Metal Cathode Organic Luminescent Layer Transparent Organic Hole Transportation Layer Indium-Tin-Oxide anode Glass Substrate Circular polarizer Molecular analogs to diluted magnetic inorganic semiconductors which are useful in spintronics

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