P. Day

University College London, Londinium, England, United Kingdom

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Publications (316)541.07 Total impact

  • Tetrahedron 10/2013; 69(14):8738. · 2.80 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 11/2010; 26(46).
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    ABSTRACT: BEDT-TTF salts have been widely studied because of their ability to combine various physical properties in the same lattice. The series of salts containing tris(oxalato)metallate anions has been widely studied and has given rise to paramagnetism, ferromagnetism, superconductivity, semiconductivity, conductivity and proton conductivity. However, one property that has not been exploited fully in this family of materials is chirality.
    Physica B Condensed Matter 06/2010; 405(11):S34. · 1.28 Impact Factor
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    ABSTRACT: In recent years, concern has been raised about the charge fluctuation of the superconducting transition in the loosely dimerized molecular conductors. Not only the observation of the charge fluctuation is of considerably important but also the understanding of the mechanism of the fluctuation. We have observed degree of charge fluctuation of several β″-type ET salts. The β″-type ET salt is one of the best model compounds because the direction of the largest inter-site Coulomb interaction is perpendicular to that of the largest transfer integral. This structural property allows us to examine the role of inter-site Coulomb interaction from the viewpoint of the inter-molecular distance. The difference in the molecular charges between the charge rich site and the charge poor sites, Δρ, is correlated with the conducting behavior; the superconducting materials have the small but finite Δρ, whereas Δρ of the insulating (metallic) materials is large (almost zero). After the analysis of the configuration in the inter-molecular distances, we have found that the degree of fluctuation, Δρ, is attributed to the number of the most stable charge distribution(s), NS, and the number of the energy levels of the allowed charge distribution, NA. The superconducting materials belong to the condition of NS≥2 and NA≥2. Indeed, this condition contributes to the fluctuation of the molecular charges.
    Physica B Condensed Matter 06/2010; 405(11):S237. · 1.28 Impact Factor
  • CrystEngComm 01/2009; 11:993. · 3.88 Impact Factor
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    ABSTRACT: We describe the synthesis, crystal structure and conducting properties of two new BEDT-TTF charge transfer salts of tris(oxalato)ferrate(III) containing slightly different numbers of water molecules, (BEDT-TTF)12[Fe(C2O4)3]2·xH2O [x = 15 (I) and 16 (II)]. I crystallizes in the monoclinic space groupC2/c, a = 36.017(10), b = 30.880(10), c = 36.183(15) Å, α = 90, β = 93.66(3), γ = 90°, V = 40161(23) Å3, T = 120(2) K, Z = 8, R1 = 0.0842 [F2 > 2σ(F2)]; II crystallizes in the same space group, a = 17.9695(15), b = 15.4988(13), c = 36.115(3) Å, α = 90, β = 93.720(2), γ = 90°, V = 10037.1(14) Å3, T = 150(2) K, Z = 4, R1 = 0.0673 [F2 > 2σ(F2)]. Electrical resistivity measurements show that I and II are semiconductors below 275 K.
    CrystEngComm 01/2008; 2:192. · 3.88 Impact Factor
  • Peter Day
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    ABSTRACT: Neutron scattering has long been the ultimate technique of choice for defining the structures and excitations in magnetically ordered solids. Hence, it is surprising that neutron diffraction has not played a larger part in the rapidly growing field of molecule-based magnets. There are several reasons for this: large-volume unit-cells, frequency of low symmetry, containing a relatively low concentration of magnetic centers meaning that the magnetic contribution is a small fraction of the total scattering while the need to deuterate the organic ligands limits the available molecules. Nevertheless, it is possible to get information about short- and long-range ordering and this brief review summarizes the recent work on contrasting molecular magnetic materials: the weakly ferromagnetic Mn(II) organo-phosphonates; the bimetallic oxalato- and dithio-oxalato-honeycomb layer ferro- and ferrimagnets and a prototype for π-d ferrimagnetism in ion-radical salts.
    Inorganica Chimica Acta - INORG CHIM ACTA. 01/2008; 361(12):3365-3370.
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    ABSTRACT: The synthesis, crystal structure and physical properties of two new BEDT-TTF charge-transfer salts containing the tris(oxalato)ferrate(III) anion are described. The most commonly found tris(oxalato)metallate(III) salts of BEDT-TTF contain alternating layers of BEDT-TTF cations and tris(oxalato)metallate anions, but the two salts reported here are multi-layered structures. Compound I is of the type ABCDABCDA as observed previously in the proton-conducting compound β″-(BEDT-TTF)4[Fe(C2O4)3]2·18-crown-6·9HxO and the alpha–beta family of salts α,β″-(BEDT-TTF)4[(NH4)Ga/Fe(C2O4)3]·G (G = PhN(CH3)COH, PhCH2CN and PhCOCH3). In α-(BEDT-TTF)9[Fe(C2O4)3]8Na18(H2O)24 (I) the A layers consist of only BEDT-TTF, B/D layers consist of tris(oxalato)ferrate(III) and sodium, and the C layers consist of sodium and water. In α-(BEDT-TTF)10(18-crown-6)6K6[Fe(C2O4)3]4(H2O)24 (II) the packing is of a type not seen before, ABCBABCBA. The A layers in II consist of only BEDT-TTF, B layers consist of tris(oxalato)ferrate(III), potassium, water and 18-crown-6, and C layers consist of 18-crown-6, potassium and water. Both salts are semiconductors between room temperature and 140 K.
    Journal of Materials Chemistry 01/2007; 31:3324. · 6.63 Impact Factor
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    ABSTRACT: The magnetic structures of crystals of NiBr2 doped with 2, 5, and 10 mol % NiCl2 are investigated by neutron diffraction and optical spectroscopy, with special reference to the incommensurate helical phase. Behaviour of the magnetic satellite reflections around (003/2) shows that the propagation vector of the helical phase is reduced from 0.15 nm−1 in NiBr2 to 0.12 nm−1 in the crystal doped with 5% NiCl2. The commensurate-incommensurate transition temperature Tic is similarly reduced, from 22.5 to 17 K. The propagation direction is unaffected by the dopant, remaining along [110]. Although no resolved magnetic satellite reflections are found in the 10% Cl− -doped crystal, a difference plot between 7 and 10 K suggests that the incommensurate phase exists below 10 K. The Néel temperatures of the samples show no significant variation with dopant concentration. The intensity of the “cold” exciton-magnon combination band between 6050 and 6100 Å, which is associated with the incommensurate phase is used to determine Tic and its behaviour in a magnetic field is used to plot magnetic phase diagrams in the Hab-T plane. No cold band is observed in the 10% Cl− -doped crystal. A hot band. resulting from the ferromagnetic component of the intraplanar coupling, is also studied.Die magnetischen Strukturen von NiBr2-Kristallen dotiert mit 2, 5 und 10 Mol% NiCl2 werden mittels Neutronenbeugung und optischer Spektroskopie untersucht, insbesondere bezüglich der incommensurablen helikalen Phase. Das Verhalten der magnetischen Satellitenreflexe um (003/2) zeigt, daß der Ausbreitungsvektor der helikalen Phase von 0,15 nm−1 in NiBr2 auf 0,12 nm−1 im mit 5% NiCl2 dotierten Kristall reduziert wird. Die Übergangstemperatur Tic des Übergangs kommensurabel-inkommensurabel wird ähnlich von 22,5 auf 17 K, reduziert. Die Ausbreitungs-richtung wird durch den Dopanden nicht beeinflußt und bleibt in Richtung [110]. Obwohl keine aufgelösten magnetischen Satellitenreflexe in den mit 10% Cl− dotierten Kristallen gefunden werden, weist eine Differenzenauftragung zwischen 7 und 10 K darauf hin, daß die inkommensurable Phase unterhalb 10 K existiert. Die Néeltemperatur der Proben zeigt keine signifikante Änderung mit der Dotierungskonzentration. Die Intensität der „kalten” Exziton-Magnon-Kombinations-bande zwischen 6050 und 6100 Å, die mit der inkommensurablen Phase verbunden ist, wird zur Bestimmung von Tic benutzt, und ihr Verhalten im Magnetfeld wird benutzt, um magnetische Phasendiagramme in der Hab-T-Ebene aufzuzeichnen. In mit 10% Cl− dotierten Kristallen werden keine kalten Banden beobachtet. Ein heißes Band, das aus der ferromagnetischen Komponente der intraplanaren Kopplung herrührt, wird ebenfalls untersucht.
    physica status solidi (b) 02/2006; 113(2):623 - 634. · 1.49 Impact Factor
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    ABSTRACT: We report high-field magnetotransport studies on quasi-two dimensional β″-(BEDT-TTF)4[(H3O)M(C2O4)3]·Y where Y is a solvent in the anionic layer. By changing the size of the solvent the low temperatures electronic behaviour varies from superconducting (for larger solvents, Y=C6H5NO2 and C6H5CN) to metallic (for smaller solvents, Y=C5H5N and CH2Cl2). These changes in the ground state are connected with modifications of the Fermi surface, which varies from having one or two pockets for the superconducting charge-transfer salts to at least four pockets in the case of metallic ones. When superconducting, the materials have very large in-plane critical fields (up to 32 T) and enhanced effective masses compared with the metallic compounds. The role of the charge-order fluctuations in stabilizing the superconducting ground state and the effects of intrinsic local disorder is discussed.
    Journal of Low Temperature Physics 01/2006; 142(3):253. · 1.18 Impact Factor
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    ABSTRACT: We report the structures and physical properties of new β′′-(BEDT-TTF)4[Fe(oxalate)3]·G salts where A = H3O+, G = PhCl; A = Rb+ G = Pyridine. The structure of the PhCl salt is isomorphous with β′′-(BEDT-TTF)4[(H3O)M(oxalate)3] with other guest molecules. PhCl is ordered in die hexagonal pockets formed by the [(H3O)Fe(oxalate)3] layer. The electrical conductivity is metallic down to 100 K, below which the resistivity increases with decreasing temperature. The specific conductivity at room temperature is about 10 S/cm. We also report the salt β′′-(BEDT-TTF)4[RbFe(oxalate)3]·Pyridine where Rb+ replaces H3O. The electrical resistivity shows metallic behavior down to 100 K. and turns up gradually to a maximum at 65 K below which the system re-enters the metallic state down to liquid helium temperature. Neither salt shows superconductivity down to 2 K. In addition, other new β′′-(BEDT-TTF)4[(H3O)M(oxalate)3]·salts with M = Cr, Ga, Fe; G = CH2Cl2, CH2ClBr, CH2Br2 are also reported.
    Synthetic Metals 09/2005; 152(1-3):373. · 2.11 Impact Factor
  • Peter Day, Eugenio Coronado
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    ABSTRACT: For Abstract see ChemInform Abstract in Full Text.
    Magnetism: Molecules to Materials V, 07/2005: pages 105 - 159; , ISBN: 9783527604388
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    E. Coronado, P Day
    Coronado, E. and Day, P. (2004) Magnetic molecular conductors. Chemical Reviews, 104 (11). pp. 5419-5448. ISSN 00092665. 01/2005;
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    Eugenio Coronado, Peter Day
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    ABSTRACT: For Abstract see ChemInform Abstract in Full Text.
    Chemical Reviews 11/2004; 104(11):5419-48. · 41.30 Impact Factor
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    ABSTRACT: A new synthesis route to the π -d ferrimagnet TTF[ Cr(NCS){4}(1,10'-phenanthroline)] is described along with recent magnetic investigations. In particular the variable frequency AC magnetisation of the protonated and fully deuterated samples indicate no frequency dependence and a Tc of 8.7 K. Single crystal heat capacity and muon spin relaxation experiments show a second magnetic transition at 2.4 K. Key words. Charge-transfer salts, conductivity, ferrimagnetism.
    Journal de Physique IV (Proceedings) 04/2004; 114(1):585-587. · 0.29 Impact Factor
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    ABSTRACT: We report high-field magnetotransport measurements on $\beta''$-(BEDT-TTF)$_4$[ (H$_3$O)M(C$_2$O$_4$)$_3$] $\cdot$ $solvent$, where M=Ga$^{3+}$, Cr$^{3+}$ and Fe$^{3+}$ and $solvent$=C$_5$H$_5$N. In spite of their differing transition metal-ions, M, the three compounds exhibit similar magnetic quantum oscillation spectra superimposed on a positive magnetoresistance. At least four independent quantum oscillation frequencies have been identified, corresponding to two different hole and electron pockets of the Fermi surface which follow the rules of a compensated metal. Observation of the small pockets could be the result of the Fermi surface reconstruction induced by a possible density wave. The effective masses are very similar for different samples and for different pockets range between $m_{\rm eff} \approx 0.5-1.1~m_e$ whereas the Dingle temperatures varies between $T_{\rm D} \approx 1.4-4$ K. At low temperature, the longitudinal magnetoresistance violates Kohler's rule, suggesting that the interlayer transport in these quasi-2D systems cannot be related to a single scattering time and that the disorder plays an important role. Key words. Magnetoresistance-quantum oscillations.
    Journal de Physique IV (Proceedings) 04/2004; 114:205. · 0.29 Impact Factor
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    ABSTRACT: We report magnetotransport measurements performed in magnetic fields of up to 33 T and at low temperatures (0.45 K<T<4.2 K) on two iso-structural superconducting charge-transfer salts, β''-(BEDT-TTF)4[ (H3O)M(C2O4)3] \cdot C6H5NO2, where the 3d metal ion M is either non-magnetic Ga3+ or magnetic Cr3+. Quantum oscillations suggest that the salt with M = Ga has two two-dimensional Fermi surface pockets (45 T and 230 T) whereas when M = Cr only one pocket (230 T) is observed. Replacing Ga with Cr has the effect of enhancing the effective mass of the 230 T pocket from 1.2 ± 0.2 me to 2.2 ± 0.3 me and reducing the superconducting critical temperature from Tc ≈ 8 K to Tc ≈ 5 K. Key words. organic superconductors-quantum oscillations.
    Journal de Physique IV (Proceedings) 04/2004; 114(1):285-287. · 0.29 Impact Factor
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    ABSTRACT: Radical ion salts of the neutral organic radicals, 2-imidazolyl nitronyl nitroxide (2-IMNN) and 2-benz- imidazolyl nitronyl nitroxide (2-BIMNN), and a diradical cation salt of pyridine-2,6-diylbis(nitronyl nitroxide) (2,6-PYBNN), were prepared. The radical ion salts of 2-BIMNN, Li$^{+}$(2-BIMNN)$^{\bullet -}$ and (2-BIMNN)$^{\bullet +}$BF$_{4}^{-}$, exhibit strong antiferromagnetic interactions with exchange coupling constants $J/k = -42$ K and -510 K, respectively, while the 2-IMNN salts show Curie-Weiss behaviour with Weiss constants $\theta = -9.0$ K for Li$^{+}$(2-IMNN)$^{\bullet -}$ and $\theta = -1.8$ K for (2-IMNN)$^{\bullet +}$Cl$^{-}$, indicating weak interactions. The diradical cation salt (2,6-PYBNN)$^{\bullet \bullet +}$Cl$^{-}$ shows intramolecular ferromagnetic interaction with $J/k = +4.7$ K and intermolecular antiferromagnetic interaction with $\theta = -0.7$ K, which is remarkably reduced from $J/k = -57$ K observed in the diradical 2,6-PYBNN. Key words. Magnetism – molecular compounds – radical ion salts.

    Journal de Physique IV (Proceedings) 01/2004; · 0.29 Impact Factor
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    Peter Day
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    ABSTRACT: A synoptic account is given of some 40 years activity in the chemistry and physics of inorganic and metal-organic solids with emphasis on optical, magnetic and superconducting properties.
    Journal of Physics and Chemistry of Solids 01/2004; 65(1):3-9. · 1.53 Impact Factor
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    ABSTRACT: We applied magneto-optical techniques to investigate the electron spin resonance (ESR) spectra of single crystal and powder samples of the organic superconductor beta''-(BEDT- TTF){4}[ (H{3}O)Fe (C{2}O{4}){3}] C{6}H{5}CN. Data were obtained in magnetic fields up to 10 Tesla using both cylindrical and rectangular resonators at 55, 63 and 72 GHz and transmission measurements at 95 and 190 GHz with field modulation. Analysis of the high field-high frequency ESR lines for different field orientations and temperatures allows the determination of the g-value anisotropy and the zero-field splitting parameters for the Fe3+ ions (S=5/2), showing that they occupy a site with distorted octahedral symmetry. The temperature and frequency dependences of the magneto-optical spectra are used to identify the nature of the interaction between localised Fe spins and between the local moments and the delocalised carriers. Key words. Electron Spin Resonance. Antiferromagnetism. Type-II superconductor. Vortex state.
    Journal de Physique IV (Proceedings) 01/2004; 114:347-349. · 0.29 Impact Factor

Publication Stats

2k Citations
541.07 Total Impact Points

Institutions

  • 2008–2010
    • University College London
      • Department of Chemistry
      Londinium, England, United Kingdom
  • 1993–2008
    • The Royal Institution of Great Britain
      Londinium, England, United Kingdom
    • Loughborough University
      • Department of Physics
      Loughborough, ENG, United Kingdom
  • 1973–2006
    • University of Oxford
      • • Department of Physics
      • • Inorganic Chemistry Laboratory
      Oxford, England, United Kingdom
  • 2005
    • University of Utah
      Salt Lake City, Utah, United States
  • 2004
    • University of Valencia
      • Instituto de Ciencia Molecular (ICMol)
      Valenza, Valencia, Spain
  • 1993–2004
    • The Royal Institution
      Londinium, England, United Kingdom
  • 2003
    • Materials Science Institute of Barcelona
      Barcino, Catalonia, Spain
  • 2000
    • University of Southampton
      Southampton, England, United Kingdom
  • 1998
    • University of Cambridge
      • Department of Physics: Cavendish Laboratory
      Cambridge, ENG, United Kingdom
  • 1985–1992
    • Institut Laue-Langevin
      Grenoble, Rhône-Alpes, France
  • 1979
    • Imperial College London
      • Department of Physics
      London, ENG, United Kingdom