scholarly journals Magnetic and Electrical Transport Properties of Vanadium Telluride

1980 ◽  
Vol 35 (7) ◽  
pp. 701-703 ◽  
Author(s):  
C. Prasad ◽  
R. A. Singh
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Magnetic Susceptibility ◽  
Electrical Transport ◽  
Powdered Sample ◽  
Neel Temperature ◽  
Electrical Transport Properties ◽  
Néel Temperature ◽  
Paramagnetic Curie Temperature ◽  
Temperature Range

Measurements of the magnetic susceptibility of a powdered sample of VTe in the temperature range 90 - 700 K, and of the a.c. electrical conductivity (σ), thermoelectric power (θ) and dielectric constant (ε′) of pressed pellets of the compound in the temperature range 300 -1100 K are reported. The compound is found to be antiferromagnetic with Neel temperature 420 ± 5 K. The effective paramagnetic moment and paramagnetic Curie temperature are found to be 1.6 μB and - 250 K, respectively. The dependence of σ, θ and ε′ on temperature shows no anomaly at the Neel temperature and is indicative of the metallic nature of the compound.

scholarly journals Der Antiferromagnetismus des Ferritins bei Messungen der magnetischen Suszeptibilität im Temperaturbereich von 4,2 bis 300°K

1965 ◽  
Vol 20 (2) ◽  
pp. 167-172 ◽  
Author(s):  
Georg Schoffa
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Structure ◽  
Magnetic Moment ◽  
Exchange Constant ◽  
Antiferromagnetic Exchange ◽  
Neel Temperature ◽  
Néel Temperature ◽  
Temperature Range ◽  
Experimental Values ◽  
Oxygen Atoms

Measurements of magnetic susceptibility in the temperature range 4.2-300°K show that ferritin is antiferromagnetic with a Néel temperature of 20° ± 3°K. The theory of J. S. SMART for antiferromagnetic exchange between iron atoms clustered in groups of two (“isolated clusters”) gives the best agreement between theoretical and experimental values. The antiferromagnetic exchange constant is J/k=- 4.8 (°K). Reduced magnetic moment for µeff =3.85 μB is due to the transfer of two electrons from oxygen atoms to ferric atoms caused on the cation-anion-cation superexchange. Some models of superexchange are discussed. Antiferromagnetism and superexchange are possibly caused on the cubic magnetic structure of iron-oxygen micelles in ferritin.

scholarly journals Pressure-Induced Structural Phase Transition and Metallization in Ga2Se3 up to 40.2 GPa under Non-Hydrostatic and Hydrostatic Environments

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 746
Author(s):  
Meiling Hong ◽  
Lidong Dai ◽  
Haiying Hu ◽  
Xinyu Zhang
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
High Pressure ◽  
Phase Transformation ◽  
Transport Properties ◽  
Electrical Transport ◽  
Structural Phase ◽  
Structure Evolution ◽  
Systematic Research ◽  
Electrical Transport Properties

A series of investigations on the structural, vibrational, and electrical transport characterizations for Ga2Se3 were conducted up to 40.2 GPa under different hydrostatic environments by virtue of Raman scattering, electrical conductivity, high-resolution transmission electron microscopy, and atomic force microscopy. Upon compression, Ga2Se3 underwent a phase transformation from the zinc-blende to NaCl-type structure at 10.6 GPa under non-hydrostatic conditions, which was manifested by the disappearance of an A mode and the noticeable discontinuities in the pressure-dependent Raman full width at half maximum (FWHMs) and electrical conductivity. Further increasing the pressure to 18.8 GPa, the semiconductor-to-metal phase transition occurred in Ga2Se3, which was evidenced by the high-pressure variable-temperature electrical conductivity measurements. However, the higher structural transition pressure point of 13.2 GPa was detected for Ga2Se3 under hydrostatic conditions, which was possibly related to the protective influence of the pressure medium. Upon decompression, the phase transformation and metallization were found to be reversible but existed in the large pressure hysteresis effect under different hydrostatic environments. Systematic research on the high-pressure structural and electrical transport properties for Ga2Se3 would be helpful to further explore the crystal structure evolution and electrical transport properties for other A2B3-type compounds.

Structure-Electrical Transport Property Relationship of Anisotropic iPP/CNT Films

2013 ◽  
Vol 1499 ◽  
Author(s):  
Parvathalu Kalakonda ◽  
Michael Daly ◽  
Kaikai Xu ◽  
Yaniel Cabrera ◽  
Robert Judith ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Transport ◽  
Preparation Method ◽  
Weight Percent ◽  
Electrical Transport Properties ◽  
Oriented Polymer ◽  
Nano Composite ◽  
Nano Structure ◽  
Relationship Of ◽  
Fine Tune

ABSTRACTThe internal micro/nano-structure of anisotropically oriented polymer/CNTs composites determines their macroscopic properties. However, the connections between the two are not fully understood. The varying of CNT concentration, preparation method, and a thermodynamic parameter (e.g. temperature) can all play interconnected role. In this work, the macroscopic electrical conductivity was measured perpendicular to the film thickness of an insulating polymer (isotactic PolyPropylene, iPP) and a nano-composite of iPP with 5 weight percent of CNT. The thin films studied were sheared (anisotropically nano-structured) and non-sheared (with random internal structure). In general the effect of melt shearing induces anisotropy on the electrical transport properties of the iPP/CNT films in directions parallel and perpendicular to the direction of orientation. Our results show that for the pure iPP, resistivity slightly increases with shear at higher temperatures. When CNTs are introduced, there is a large difference between the resistivity of the sheared and non-sheared nanocomposite. The sheared PNCs when the CNTs are aligned parallel to each other, have higher resistivity, which is possibly due to the higher concentration at which the percolation threshold occurs in this arrangement. The resistivity decreases overall, as the temperature increases from 0 to 50 °C. These results show that CNTs can be used to control and fine tune the desired macroscopic physical properties of nanocomposites, by concentration and orientation, such as electrical conductivity, for applications where such properties are necessary.

scholarly journals Characteristics of Coherent Optical Phonons in a Hexagonal YMnO3 Thin Film

2019 ◽  
Vol 9 (4) ◽  
pp. 704 ◽  
Author(s):  
Takayuki Hasegawa
Keyword(s):  
Thin Film ◽  
Optical Phonon ◽  
Laser Pulses ◽  
Generation Process ◽  
Neel Temperature ◽  
Optical Phonons ◽  
Néel Temperature ◽  
Temperature Range ◽  
Lower Temperature Range ◽  
Lower Temperature

This paper reviews our recent study on a coherent optical phonon in a hexagonal YMnO3 thin film together with related optical studies in hexagonal RMnO3 (R = Y, Lu, Ho) compounds. Coherent phonons have been observed in RMnO3 compounds by pump-probe spectroscopy with subpicosecond laser pulses, whereas the observation of coherent optical phonons was reported only in LuMnO3. Recently, we succeeded in the observation of the coherent optical phonon in a YMnO3 thin film. The generation process of the coherent optical phonon is assigned to a displacive mechanism, which is identical to that in LuMnO3. The coherent optical phonon is observed in the temperature range from 10 K to room temperature, while the oscillation intensity strongly decreases as the temperature increases to the Néel temperature of ~70 K from a lower temperature range. It is interesting that the temperature dependence is largely different from that in LuMnO3. We describe that the result can be qualitatively explained by the property of an isostructural transition around the Néel temperature in RMnO3 compounds. In addition, we briefly discuss ultrafast incoherent responses of excited electronic states from the viewpoint of the excitation photon energy of laser pulses.

scholarly journals Potassium-Doped Para-Terphenyl: Structure, Electrical Transport Properties and Possible Signatures of a Superconducting Transition

2020 ◽  
Vol 5 (4) ◽  
pp. 78
Author(s):  
Nicola Pinto ◽  
Corrado Di Nicola ◽  
Angela Trapananti ◽  
Marco Minicucci ◽  
Andrea Di Cicco ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Electrical Transport ◽  
Low Temperatures ◽  
Chemical Method ◽  
Preliminary Evidence ◽  
Superconducting Gap ◽  
Superconducting Transition ◽  
Electrical Transport Properties ◽  
High Tc ◽  
Resistivity Measurements

Preliminary evidence for the occurrence of high-TC superconductivity in alkali-doped organic materials, such as potassium-doped p-terphenyl (KPT), were recently obtained by magnetic susceptibility measurements and by the opening of a large superconducting gap as measured by ARPES and STM techniques. In this work, KPT samples have been synthesized by a chemical method and characterized by low-temperature Raman scattering and resistivity measurements. Here, we report the occurrence of a resistivity drop of more than 4 orders of magnitude at low temperatures in KPT samples in the form of compressed powder. This fact was interpreted as a possible sign of a broad superconducting transition taking place below 90 K in granular KPT. The granular nature of the KPT system appears to be also related to the 20 K broadening of the resistivity drop around the critical temperature.

Computational Analysis of Strain Effects on Electrical Transport Properties of Crystalline Nanocomposite Thin Films

2011 ◽  
Author(s):  
Hua Li ◽  
Gang Li
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Band Structure ◽  
Transport Properties ◽  
Electrical Transport ◽  
Electronic Band Structure ◽  
Electrical Transport Properties ◽  
Electronic Band ◽  
Strain Effects ◽  
Nanocomposite Thin Films

In this work, we model the strain effects on the electrical transport properties of Si/Ge nanocomposite thin films. We utilize a two-band k·p theory to calculate the variation of the electronic band structure as a function of externally applied strains. By using the modified electronic band structure, electrical conductivity of the Si/Ge nanocomposites is calculated through a self-consistent electron transport analysis, where a nonequilibrium Green’s function (NEGF) is coupled with the Poisson equation. The results show that both the tensile uniaxial and biaxial strains increase the electrical conductivity of Si/Ge nanocomposite. The effects are more evident in the biaxial strain cases.

Thermoelectric properties of polycrystalline Bi2Se3−x by powder compaction sintering

2020 ◽  
Vol 34 (18) ◽  
pp. 2050206
Author(s):  
Ying Zhou ◽  
Zhenhua Ge ◽  
Jun Guo ◽  
Jing Feng
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Carrier Concentration ◽  
Thermoelectric Properties ◽  
Thermoelectric Materials ◽  
Electrical Transport ◽  
Bulk Material ◽  
Powder Compaction ◽  
Electrical Transport Properties ◽  
X Ray

[Formula: see text] is a [Formula: see text] compound (where Pn = Bi and Sb, Ch = Te, Se, and S), which has attracted increasing attention as a candidate for use in thermoelectric applications. Previous studies demonstrated the advantage of [Formula: see text] thermoelectric materials, despite an inferior thermoelectric performance. Herein, a series of [Formula: see text] ([Formula: see text], 0.10, 0.15, 0.20, and 0.25) thermoelectric materials were prepared by powder compaction sintering. The effects of phase structures and microstructure of the [Formula: see text] bulk material were analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The thermoelectric properties, including Seebeck coefficient, electrical conductivity, and thermal conductivity, were measured systematically. The results show that carrier concentration increased with decreasing Se content, which in turn affected the electrical transport properties. Low Se contents gave larger power factor (PF) values than the pristine [Formula: see text] sample, the maximum PF value being [Formula: see text] at 320 K for [Formula: see text]. The variation in PF was attributed to the variations in electrical conductivity [Formula: see text] and Seebeck coefficient [Formula: see text] upon optimizing Se content. The [Formula: see text] samples showed an enhanced thermoelectric figure of merit (ZT) with increasing measurement temperature, due to the increased [Formula: see text] value, [Formula: see text], and decreased [Formula: see text]. The [Formula: see text] sample exhibited the highest ZT (0.28) at 575 K, while [Formula: see text] exhibited the lowest ZT (0.14) at 325 K. This indicated that tuning Se content was an effective way to enhance carrier concentration.

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