Search results for "Electrical resistivity and conductivity"
showing 10 items of 317 documents
Electronic properties of *-oriented thin films
2007
Abstract To perform high precision measurements of the transport anisotropy, epitaxial, a *-oriented thin films of UPd 2 Al 3 have been prepared on LaAlO 3 (1 1 0) substrates. The critical temperature T c ≈ 1.75 K and the upper critical field B c 2 ≈ 3 T are comparable to typical bulk values. In contrast to UNi 2 Al 3 , we observed only a weak anisotropy in directional resistivity measurements, especially no dependence of the superconducting transition temperature on the direction of the applied current. Hall effect measurements show two characteristic minima at T = 16 K ≈ T N and T ≈ 6 K , which corresponds to features seen in earlier measurements on c *-oriented films.
Temperature Dependence of Electronic and Magnetic Properties of (DOEO)<sub>4</sub>[HgBr<sub>4</sub>]·TCE Single Crystals
2015
The temperature dependence of electronic and magnetic properties of the organic charge-transfer salt (DOEO)4[HgBr4]·TCE was investigated using magnetometry. The magnetic susceptibility shows a maximum at 40 K followed by an onset of a pronounced increase at 70 K and a constant behavior above 120 K. Implications on the charge carrier density are discussed. Combining the magnetometry with resistivity and ESR measurements we propose a sequence of insulating, metallic and semiconducting behavior with increasing temperature. Our results indicate that (DOEO)4[HgBr4]·TCE is close to the boundary between an insulating and conducting ground state.
Tuning the carrier concentration for thermoelectrical application in the quaternary Heusler compound Co2TiAl(1−x)Six
2010
The family of half-metallic ferromagnets Co2TiZ exhibits exceptional transport properties. The investigated compounds Co2TiAl(1−x)Six (x = 0.25, 0.5, 0.75) show Curie temperatures (TCs) that vary between 250 and 350 K, depending on the composition. Above TC the Seebeck coefficient remains constant. This makes them promising candidates for thermoelectric devices such as thermocouples with a tunable working range. The electrical resistivity data show an anomaly at TC which is attributed to changes in the electronic structure and therefore in the carrier concentration.
Impedance spectroscopy studies of SrMnO3, BaMnO3and Ba0.5Sr0.5MnO3ceramics
2014
The impedance spectrum of hexagonal SrMnO3, rhombohedral BaMnO3 and orthorhombic Ba0.5Sr0.5MnO3 ceramics, synthesized by conventional high-temperature method, was studied in a wide temperature and frequency range. The complex impedance plots of Z″ versus Z′ pointed to two contributions originating from grains and grain boundaries. The parameters of electric equivalent circuit were calculated. The semicircles related to the grain boundary are located at the lower frequency side due to higher resistivity and capacity of the grain boundaries. The Ba0.5Sr0.5MnO3 ceramics is characterized by the lowest activation energy related to the grains. The conductivities σac of all the investigated sample…
Conductivity of the two-dimensional electron gas atLaAlO3/SrTiO3interface
2017
We propose an analytical theory of metallic conductivity in the two-dimensional (2D) ${\mathrm{LaAlO}}_{3}/{\mathrm{SrTiO}}_{3}$ (LAO/STO) interface. For that we consider the electron-phonon interaction at the interface. The electronic part is taken from our previous work [Phys. Chem. Chem. Phys. 18, 2104 (2016)], considering the conditions for the interfacial charge carrier (electron or hole) to become itinerant. The second ingredient deals with the atomic oscillations localized near the interface and decaying rapidly at its both sides, which can be regarded as 2D acoustic phonons. The dispersion of such phonons depends on the characteristics of phonon spectra of LAO and STO. Calculating t…
Structural characterization and anomalous Hall effect of Rh2MnGe thin films
2015
Abstract We present the preparation, structural investigations, and transport properties of L21-ordered epitaxial Rh2MnGe Heusler thin films grown by pulsed laser deposition. The films grow (1 0 0) oriented on (1 0 0)MgO substrate with [ 0 1 1 ] Rh 2 MnGe ∥ [ 0 1 0 ] MgO . The rocking curve widths of (4 0 0) reflections are below 1° and decrease with increasing deposition temperature. The flat surface of the thin films allowed lithographic patterning enabling quantitative magnetotransport measurements. We measured resistivity and the Hall effect. We suggest skew scattering as the dominant effect in the temperature dependent anomalous Hall effect, consistent with the theoretically expected s…
Finite range scattering of Ni and Zn impurities in Y-123 thin films
1997
Abstract We investigated YBa 2 (Cu 1− z M z ) 3 O 7-δ (M Ni,Zn) thin films and determined the decrease of T c and the increase of residual resistivity due to Cu-site substitution, taking into account the CuO-chain contributions to the total conductivity. Although Zn suppresses T c stronger than Ni by a factor of 2.3 the increase of resistivity differs only slightly. Furthermore the observed resistivities are too high to be explained within scattering from point-like defects. To reconcile these contradictions, we assumed finite size scattering potentials, which lead to scattering phase shifts δ l of higher angular momebtum l > 0. T c -suppression is discussed qalitatively within this picture.
Electrical Transport Properties of Lead−Free (Na0.5Bi0.5)1-xBaxZr0.04Ti0.96O3Ceramics (x = 0.06, 0.085, 0.1)
2011
Lead-free ceramics (Na0.5Bi0.5)1-xBaxZr0.04Ti0.96O3 were prepared by solid phase hot pressing sintering process. Density values of obtained samples are higher than 95% of the theoretical ones. Samples with x = 0.06, 0.085 and 0.1 were investigated in the present work. For these samples both ac and dc electric conductivity were studied. A low frequency (100 Hz-100 kHz) ac conductivity obeys the power law, characteristic for disordered materials. The dc conductivity has a thermally activated character. A barrier hopping model is found to explain the mechanism of charge transport in these materials. The (Na0.5Bi0.5)1-xBaxZr0.04Ti0.96O3 system is expected to be a new and promising candidate for…
Temperature-dependent resistivity and anomalous Hall effect in NiMnSb from first principles
2019
We present implementation of the alloy analogy model within fully relativistic density-functional theory with the coherent potential approximation for a treatment of nonzero temperatures. We calculate contributions of phonons and magnetic and chemical disorder to the temperature-dependent resistivity, anomalous Hall conductivity (AHC), and spin-resolved conductivity in ferromagnetic half-Heusler NiMnSb. Our electrical transport calculations with combined scattering effects agree well with experimental literature for Ni-rich NiMnSb with 1--2% Ni impurities on Mn sublattice. The calculated AHC is dominated by the Fermi surface term in the Kubo-Bastin formula. Moreover, the AHC as a function o…
Tailoring of the electrical and thermal properties using ultra-short period non-symmetric superlattices
2016
Thermoelectric modules based on half-Heusler compounds offer a cheap and clean way to create eco-friendly electrical energy from waste heat. Here we study the impact of the period composition on the electrical and thermal properties in non-symmetric superlattices, where the ratio of components varies according to (TiNiSn)���:(HfNiSn)���������, and 0 ��� n ��� 6 unit cells. The thermal conductivity (��) showed a strong dependence on the material content achieving a minimum value for n = 3, whereas the highest value of the figure of merit ZT was achieved for n = 4. The measured �� can be well modeled using non-symmetric strain relaxation applied to the model of the series of thermal resistanc…