MODIFICATION OF NORMAL-STATE AND SUPERCONDUCTING PROPERTIES OF HIGH-Tc OXIDES VIA TREATMENT BY METAL-PHTHALOCYANINES

Exposure of Bi- or Tl-based high-T c oxide powders to vapors of metal-phthalocyanines MPc (M is Zn or Ni) resulted in the formation of a family of new compounds with modified crystal lattice parameters, electronic structure, phonon spectrum and magnetic properties as compared to the starting materials. Based on the combined X ray diffraction, scanning tunneling microscopy, optical, FT–IR and microwave absorption data, a model of crystal structure is proposed where the key feature is intercalation of MPc molecules between the Bi-O (Tl-O) bilayers. Values of dc magnetization at 300 K varied over two orders of magnitude as a function of chemical composition and nature of the central metal ion in MPc. Measurements of temperature dependence of magnetization of the intercalated samples revealed a divergence at low temperatures between the zero-field and the field-cooled cycles, though of lower magnitude as compared to the starting high-T c oxides. The results of this study suggest that treatment by MPc offers a possibility of controllable variation of key properties of high-T c oxides.

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Stm Studies at Electrochemically Controlled Interfaces

MRS Proceedings ◽

10.1557/proc-332-393 ◽

1994 ◽

Vol 332 ◽

Author(s):

S.M. Lindsay ◽

J. Pan ◽

T.W. Jing

Keyword(s):

Electron Tunneling ◽

Point Contact ◽

Localized States ◽

Scanning Tunneling ◽

Zero Field ◽

Tunneling Microscopy ◽

Dna Oligomers ◽

Synthetic Dna ◽

Quantum Point

ABSTRACTWe use electrochemical methods to control the adsorption of molecules onto an electrode for imaging in-situ by scanning tunneling microscopy. Measurements of the barrier for electron tunneling show that the mechanism of electron transfer differs from vacuum tunneling. Barriers depend upon the direction of electron tunneling, indicating the presence of permanently aligned dipoles in the tunnel gap. We attribute a sharp dip in the barrier near zero field to induced polarization. We propose a ‘tunneling’ process consisting of two parts: One is delocalization of quantum-coherent states in parts of the molecular adlayer that hybridize strongly (interaction ≥ kT) with Bloch states in the metal. This gives rise to a quantum-point-contact conductance, Gc ≤ 2e2/h at a height zo. The other part comes from the exponential decay of the tails of localized states, G = Gc exp{−2K(z − z0)}. Because measured decay lengths, (2K‘)−1, are small (≈ 1 Å), STM contrast is dominated by the contour along which G[z0 (x,y)] = Gc. Measured changes in z0 are used to calculate images which are in reasonable agreement with observations. We illustrate this with images of synthetic DNA oligomers.

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Scanning Tunneling Microscopy of Metal Phthalocyanines: d6and d8Cases

The Journal of Physical Chemistry B ◽

10.1021/jp9707448 ◽

1997 ◽

Vol 101 (27) ◽

pp. 5391-5396 ◽

Cited By ~ 198

Author(s):

Xing Lu ◽

K. W. Hipps

Keyword(s):

Scanning Tunneling Microscopy ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Metal Phthalocyanines

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Synthesis and Characterization of the Heptanuclear [MnIII 6 CoIII]3+ Triplesalen Complex: Evidence for Exchange Pathways Involving Low-spin CoIII

Zeitschrift für Naturforschung B ◽

10.1515/znb-2010-0311 ◽

2010 ◽

Vol 65 (3) ◽

pp. 295-303 ◽

Cited By ~ 29

Author(s):

Erich Krickemeyer ◽

Veronika Hoeke ◽

Anja Stammler ◽

Jürgen Schnack ◽

Hartmut Bögge ◽

...

Keyword(s):

Exchange Interaction ◽

Metal Ion ◽

Magnetic Measurements ◽

Variable Temperature ◽

Molecular Structures ◽

Magnetic Data ◽

Zero Field ◽

Central Metal ◽

Zero Field Splitting ◽

Isotropic Exchange

The reaction of the tert-butyl-substituted triplesalen ligand H6talent-Bu2 with MnII(OAc)2・ 4H2O and K3[CoIII(CN)6] results in the formation of the heptanuclear complex [{(talent-Bu2 )- (MnIII(MeOH))3}2{CoIII(CN)6}](PF6)2(OAc)・11MeOH ([MnIII6 CoIII](PF6)2(OAc)・11MeOH, 1 ・11MeOH), which has been characterized by FT-IR spectroscopy, elemental analysis, ESI-MS, single-crystal X-ray diffraction, and magnetic measurements. The molecular structure of the [MnIII6 CoIII]3+ complex is closely related to the already published analogs [MnIII6CrIII]3+ and [MnIII6 FeIII]3+. Variable-temperature variable-field and μeff vs. T magnetic data have been analyzed in detail by full-matrix diagonalization of the appropriate spin-Hamiltonian consisting of isotropic exchange, zero-field splitting, and Zeeman interaction, taking into account the relative orientation of the D tensors. This allowed a careful inspection of the MnIII-MnIII exchange interaction involving a diamagnetic central metal ion. A satisfactory reproduction of the magnetic data required the incorporation not only of an exchange interaction between the MnIII ions belonging to one triplesalen half unit, but also of an exchange coupling between MnIII ions belonging to different triplesalen subunits. Satisfactory reproduction of the experimental data has been obtained for the parameter set J1 = −(0.50±0.04) cm−1, J2 = +(0.05±0.02) cm−1, and D = −(2.5±0.5) cm−1. A detailed analysis of the J1 coupling taking into account the molecular structures of the three available heptanuclear complexes [MnIII6MIII]3+ (M = Cr, Fe, Co) indicates that the exchange interaction between the MnIII ions belonging to the same triplesalen subunit involves not only an exchange pathway through the central phloroglucinol unit but also an exchange pathway through the central metal ion.

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Formation of (FeCl3)@phenylazomethine dendrimer (DPA): Fine control of the release and encapsulation of Fe ions in dendrimers

Pure and Applied Chemistry ◽

10.1351/pac-con-09-01-13 ◽

2009 ◽

Vol 81 (12) ◽

pp. 2253-2263

Author(s):

Kimihisa Yamamoto ◽

Reina Nakajima ◽

Yousuke Ochi ◽

Masanori Tsuruta ◽

Masayoshi Higuchi ◽

...

Keyword(s):

Metal Ion ◽

Scanning Tunneling ◽

Uniform Structure ◽

Research Groups ◽

Tunneling Microscopy ◽

Precise Control ◽

Oriented Film ◽

Successful Attempt ◽

Fine Control ◽

Fe Ions

Phenylazomethine dendrimers (DPAs) act as a strong coordination site for metal ion assembly. DPA G4 is regarded as a molecular capsule having 30 metal-assembling sites with a 2.7 nm diameter. We have reported the radial stepwise complexation with Sn2+ ions in the dendrimers, which means the location and number of metal ions can be controlled. Therefore, DPA G4 should realize a ferritin-like redox nanocapsule with precise control of the number of Fe ions. On the other hand, the Fe ion is a typical paramagnetic molecule. For creating an advanced memory with a high density, ferritin is one of the candidates for use as a magnetic quantum dot. Many attempts to use biomaterials, for example, ferritins and chapero-nins, as metal storage capsules have been demonstrated. Some research groups fabricate a device by assembling ferritins on a plate using their rigid and uniform structure. The attempts to use dendrimers have also been demonstrated. We now describe the successful attempt to control the "encapsulation and release" of iron ions in a dendrimer in order to mimic a ferritin through the redox reaction. Furthermore, the assembling structures of (FeCl3)n@DPA on a plate were first observed by scanning tunneling microscopy (STM) as a dendrimer complex, which shows that a highly oriented film is formed on a plate only by solvent casting.

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Zero-field skyrmionic states and in-field edge-skyrmions induced by boundary tuning

Communications Physics ◽

10.1038/s42005-021-00796-w ◽

2022 ◽

Vol 5 (1) ◽

Author(s):

Jonas Spethmann ◽

Elena Y. Vedmedenko ◽

Roland Wiesendanger ◽

André Kubetzka ◽

Kirsten von Bergmann

Keyword(s):

Spin Dynamics ◽

Transverse Component ◽

Scanning Tunneling ◽

Zero Field ◽

Tunneling Microscopy ◽

Pinning Effect ◽

Field Edge ◽

Dynamics Simulations ◽

Magnetic Skyrmions ◽

Edge Spin

AbstractWhen magnetic skyrmions are moved via currents, they do not strictly travel along the path of the current, instead their motion also gains a transverse component. This so-called skyrmion Hall effect can be detrimental in potential skyrmion devices because it drives skyrmions towards the edge of their hosting material where they face potential annihilation. Here we experimentally modify a skyrmion model system—an atomic Pd/Fe bilayer on Ir(111)—by decorating the film edge with ferromagnetic Co/Fe patches. Employing spin-polarized scanning tunneling microscopy, we demonstrate that this ferromagnetic rim prevents skyrmion annihilation at the film edge and stabilizes skyrmions and target states in zero field. Furthermore, in an external magnetic field the Co/Fe rim can give rise to skyrmions pinned to the film edge. Spin dynamics simulations reveal how a combination of different attractive and repulsive skyrmion-edge interactions can induce such an edge-pinning effect for skyrmions.

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Investigation of the Zero-Field Splitting of d8 Ions in Pseudo-tetragonal Ni(II) Compounds

Zeitschrift für Naturforschung A ◽

10.1515/zna-1994-1102 ◽

1994 ◽

Vol 49 (11) ◽

pp. 1013-1015 ◽

Cited By ~ 2

Author(s):

Jia-Jun Chen ◽

Mao-Lu Du ◽

Zhao-Ming Li

Keyword(s):

Metal Ion ◽

Tetragonal Symmetry ◽

Zero Field ◽

Central Metal ◽

Spin Orbit Coupling ◽

Cluster Approach ◽

Zero Field Splitting ◽

Field Splitting ◽

Central Transition ◽

Ion Yields

Abstract This paper presents a cluster approach to the zero-field splitting (ZFS) of the ground state 3A2(F) of d8 ions with tetragonal symmetry, in which not only the spin-orbit coupling of the central transition-metal-ion but also that of ligands contributes. For some pseudo-tetragonal Ni(II) com pounds the calculated values of the ZFS parameter follow the order Cl-> Br-> I-. This agrees with the experimental finding, while the pure crystal field approach considering only the coupling of central metal ion yields the opposite trend.

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NiPC/Si(111)(7 × 7) STUDIED WITH XPS, STM AND TAPPING MODE AIR AFM

Surface Review and Letters ◽

10.1142/s0218625x97000109 ◽

1997 ◽

Vol 04 (01) ◽

pp. 59-64 ◽

Cited By ~ 14

Author(s):

L. OTTAVIANO ◽

S. di Nardo ◽

L. LOZZI ◽

M. PASSACANTANDO ◽

P. PICOZZI ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Soft Materials ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Metal Phthalocyanines ◽

Tapping Mode ◽

Nickel Phthalocyanine ◽

Atomic Force ◽

Structural And Electronic Properties

We evaporated a few angstroms of nickel phthalocyanine (NiPC) in ultrahigh vacuum (UHV) on clean single crystal substrates of Si (111)(7×7) and studied in situ the structural and electronic properties of the interface with X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). The mesoscopic morphology of the samples has also been studied in air with a tapping mode atomic force microscope (TM-AFM). XPS measurements with variation of the NiPC thickness suggest planar adsorption of the first layer of admolecules; in particular, we found evidences for stronger chemisorption at the outer benzene rings of the PC molecule. UHV STM measurements confirm the XPS results; despite the lack of intermolecular resolution we show an image suggesting chemisorption commensurate with the substrate lattice and planar stacking consistent with the intermolecular stacking in the known crystalline phases of metal phthalocyanines. TM-AFM shows a growth mode in terms of flat islands of 20–35 Å typical height and a few hundreds of nm width. The potential of imaging with TM-AFM elastic sample properties of soft materials deposited on hard substrates is addressed.

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Synthesis and characterization of novel phthalocyanines with nitrone substituents

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424607000060 ◽

2007 ◽

Vol 11 (01) ◽

pp. 42-49 ◽

Cited By ~ 2

Author(s):

B. Narayana Achar ◽

T. M. Mohan Kumar

Keyword(s):

Electrical Conductivity ◽

Metal Ion ◽

Activation Parameters ◽

Central Metal ◽

Metal Phthalocyanines ◽

Lattice Constants ◽

X Ray Crystallography ◽

Uv Visible ◽

First Time

A novel series of nitrone-substituted, metal phthalocyanine complexes (the central metal ion being Co , Ni and Cu , respectively) were synthesized for the first time in pure state with quantitative yield. These complexes were characterized using elemental analysis, UV-visible, IR-spectroscopy, magnetic susceptibility, X-ray crystallography, and thermogravimetry. All three complexes had a monoclinic structure with different crystal lattice constants. Horowitz-Metzger, Coats-Redfern and Broido's relations were employed to calculate the kinetic and activation parameters associated with the thermal decomposition of the above complexes. Electrical conductivity studies were undertaken for all three complexes using a two-probe technique in the temperature range 30-200°C. They showed an improvement of 103-105 times the electrical conductivity at room temperature, compared to the corresponding unsubstituted metal phthalocyanines.

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