Journal articles: 'Magnetotransport experiments'

1

Hirler, F., J. Smoliner, E. Gornik, G. Weimann, and W. Schlapp. "Energy levels in quantum wires studied by tunneling and magnetotransport experiments." Applied Physics Letters 57, no. 3 (July 16, 1990): 261–63. http://dx.doi.org/10.1063/1.103708.

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Hilke, Michael, Mathieu Massicotte, Eric Whiteway, and Victor Yu. "Weak Localization in Graphene: Theory, Simulations, and Experiments." Scientific World Journal 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/737296.

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We provide a comprehensive picture of magnetotransport in graphene monolayers in the limit of nonquantizing magnetic fields. We discuss the effects of two-carrier transport, weak localization, weak antilocalization, and strong localization for graphene devices of various mobilities, through theory, experiments, and numerical simulations. In particular, we observe a minimum in the weak localization and strong localization length reminiscent of the minimum in the conductivity, which allows us to make the connection between weak and strong localization. This provides a unified framework for both localizations, which explains the observed experimental features. We compare these results to numerical simulation and find a remarkable agreement between theory, experiment, and numerics. Various graphene devices were used in this study, including graphene on different substrates, such as glass and silicon, as well as low and high mobility devices.

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Gracia-Abad, Rubén, Soraya Sangiao, Chiara Bigi, Sandeep Kumar Chaluvadi, Pasquale Orgiani, and José María De Teresa. "Omnipresence of Weak Antilocalization (WAL) in Bi2Se3 Thin Films: A Review on Its Origin." Nanomaterials 11, no. 5 (April 22, 2021): 1077. http://dx.doi.org/10.3390/nano11051077.

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Topological insulators are materials with time-reversal symmetric states of matter in which an insulating bulk is surrounded by protected Dirac-like edge or surface states. Among topological insulators, Bi2Se3 has attracted special attention due to its simple surface band structure and its relatively large band gap that should enhance the contribution of its surface to transport, which is usually masked by the appearance of defects. In order to avoid this difficulty, several features characteristic of topological insulators in the quantum regime, such as the weak-antilocalization effect, can be explored through magnetotransport experiments carried out on thin films of this material. Here, we review the existing literature on the magnetotransport properties of Bi2Se3 thin films, paying thorough attention to the weak-antilocalization effect, which is omnipresent no matter the film quality. We carefully follow the different situations found in reported experiments, from the most ideal situations, with a strong surface contribution, towards more realistic cases where the bulk contribution dominates. We have compared the transport data found in literature to shed light on the intrinsic properties of Bi2Se3, finding a clear relationship between the mobility and the phase coherence length of the films that could trigger further experiments on transport in topological systems.

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KILLI, MATTHEW, SI WU, and ARUN PARAMEKANTI. "GRAPHENE: KINKS, SUPERLATTICES, LANDAU LEVELS AND MAGNETOTRANSPORT." International Journal of Modern Physics B 26, no. 21 (July 18, 2012): 1242007. http://dx.doi.org/10.1142/s0217979212420076.

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We review recent work on superlattices in monolayer and bilayer graphene. We highlight the role of the quasiparticle chirality in generating new Dirac fermion modes with tunable anisotropic velocities in one dimensional (1D) superlattices in both monolayer and bilayer graphene. We discuss the structure of the Landau levels and magnetotransport in such superlattices over a wide range of perpendicular (orbital) magnetic fields. In monolayer graphene, we show that an orbital magnetic field can reverse the anisotropy of the transport imposed by the superlattice potential, suggesting possible switching-type device applications. We also consider topological modes localized at a kink in an electric field applied perpendicular to bilayer graphene, and show how interactions convert these modes into a two-band Luttinger liquid with tunable Luttinger parameters. The band structures of electric field superlattices in bilayer graphene (with or without a magnetic field) are shown to arise naturally from a coupled array of such topological modes. We briefly review some bandstructure results for 2D superlattices. We conclude with a discussion of recent tunneling and transport experiments and point out open issues.

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GRYGLAS, M., M. BAJ, B. JOUAULT, A. RAYMOND, C. CHAUBET, B. CHENAUD, J. L. ROBERT, and G. FAINI. "2DEG SPECTROSCOPY WITH RESONANT TUNNELING THROUGH SINGLE IMPURITY STATE." International Journal of Nanoscience 02, no. 06 (December 2003): 585–92. http://dx.doi.org/10.1142/s0219581x0300170x.

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We have used silicon impurities in an aluminum arsenide barrier to probe an adjacent two-dimensional electron gas (2DEG). A single impurity acts as a local spectrometer and scans the local density of states of the 2DEG. Magnetotransport experiments have been performed at low temperature with a magnetic field B applied along the direction of the current. Current–voltage characteristics strongly depend on B and reveal the formation of Landau levels (LLs).

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Schmidt, P. E., E. Barbier, M. Rossmanith, and M. Dobers. "Low‐temperature magnetotransport experiments in pseudomorphic GaAs/Ga0.87In0.13As/Al0.40Ga0.60As semiconductor‐insulator‐semiconductor field‐effect transistors." Applied Physics Letters 59, no. 11 (September 9, 1991): 1320–22. http://dx.doi.org/10.1063/1.105487.

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FUJITA, SHIGEJI, NEBI DEMEZ, JEONG-HYUK KIM, and H. C. HO. "MAGNETORESISTANCE IN COPPER." International Journal of Modern Physics B 22, no. 25n26 (October 20, 2008): 4434–41. http://dx.doi.org/10.1142/s0217979208050188.

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The motion of the guiding center of magnetic circulation generates a charge transport. By applying kinetic theory to the guiding center motion, an expression for the magnetoconductivity σ is obtained: σ = e2ncτ/M*, where M* is the magnetotransport mass distinct from the cyclotron mass, nc the density of the conduction electrons, and τ the relaxation time. The density nc depends on the magnetic field direction relative to copper's fcc lattice, when Cu's Fermi surface is nonspherical with “necks”. The anisotropic magnetoresistance is analyzed based on a one-parameter model, and compared with experiments. A good fit is obtained.

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ZIMBOVSKAYA, NATALYA, GODFREY GUMBS, and JOSEPH L. BIRMAN. "THEORY OF THE DC MAGNETOTRANSPORT IN LATERALLY MODULATED QUANTUM HALL SYSTEMS NEAR FILLING ν=½." International Journal of Modern Physics B 18, no. 10n11 (April 30, 2004): 1581–94. http://dx.doi.org/10.1142/s0217979204024793.

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A quasiclassical theory for DC magnetotransport in a modulated quantum Hall system near filling factor ν=½ is presented. A weak one-dimensional electrostatic potential acts on the two-dimensional electron gas. Closed form analytic expressions are obtained for the resistivity ρ⊥ corresponding to a current at right angles to the direction of the modulation lines as well as a smaller component ρ‖ for a current along the direction of the modulation lines. It is shown that both resistivity components are affected by the presence of the modulation. Numerical results are presented for ρ⊥ and ρ‖ and show reasonable agreement with the results of recent experiments.

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LEWIS, R. A., W. XU, P. M. KOENRAAD, and I. V. BRADLEY. "EFFECT OF STRONG TERAHERTZ RADIATION ON MAGNETOCONDUCTIVITY IN TWO DIMENSIONS." International Journal of Modern Physics B 16, no. 20n22 (August 30, 2002): 2964–67. http://dx.doi.org/10.1142/s0217979202013328.

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The interaction between strong THz radiation from a free electron laser and an electron sheet in a high-mobility, low-density, GaAs/AlGaAs structure has been investigated in magnetotransport experiments over a wide range of wavelengths, intensities, magnetic fields, and temperatures. Photovoltage and photocurrent effects are evident in both longitudinal and transverse potential differences. Broad cyclotron resonance is observed to high temperature and connected with a decrease in electron density. The change in electron temperature under THz radiation is estimated from changes in the magnitude of the magnetoresistivity oscillations at low lattice temperature. The effect of the magnetic field is to suppress the rise in electron temperature relative to the zero field case.

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10

Greene, S. K., J. Singleton, P. Sobkowicz, T. D. Golding, M. Pepper, J. A. A. J. Perenboom, and J. Dinan. "Subband occupancies and zero-field spin splitting in InSb-CdTe heterojunctions: magnetotransport experiments and self-consistent calculations." Semiconductor Science and Technology 7, no. 11 (November 1, 1992): 1377–85. http://dx.doi.org/10.1088/0268-1242/7/11/016.

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11

Papaioannou, E. Th, V. Karoutsos, M. Angelakeris, O. Valassiades, P. Fumagalli, N. K. Flevaris, and P. Poulopoulos. "Magnetic, Magneto-optic and Magnetotransport Properties of Nanocrystalline Co/Au Multilayers with Ultrathin Au Interlayers." Journal of Nanoscience and Nanotechnology 8, no. 9 (September 1, 2008): 4323–28. http://dx.doi.org/10.1166/jnn.2008.290.

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A series of nanocrystalline Co/Au multilayers with ultrathin Au interlayers was grown at room temperature by electron beam evaporation on Si(111), glass and polyimide substrates. X-ray diffraction measurements reveal a face centered cubic multilayered structure with very small nanograins within 7–10 nm in diameter. Magneto-optic polar Kerr effect experiments show an enhancement of the Kerr rotation around 3 eV as the Au interlayer thickness increases. The experimental data are interpreted with the help of simulated Kerr spectra. The magnetization curves and magnetic force microscopy images indicate the existence of perpendicularly magnetized stripe-domain structures at remanence. The magnitude of the magnetoresistance ratio reaches values of 0.4%. The investigation of the interplay between magnetic and magnetotransport properties demonstrates the contribution of the domain-wall spin-dependent scattering to the magnetoresistance.

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12

Cooper, Daniel R., Benjamin D’Anjou, Nageswara Ghattamaneni, Benjamin Harack, Michael Hilke, Alexandre Horth, Norberto Majlis, et al. "Experimental Review of Graphene." ISRN Condensed Matter Physics 2012 (April 26, 2012): 1–56. http://dx.doi.org/10.5402/2012/501686.

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This review examines the properties of graphene from an experimental perspective. The intent is to review the most important experimental results at a level of detail appropriate for new graduate students who are interested in a general overview of the fascinating properties of graphene. While some introductory theoretical concepts are provided, including a discussion of the electronic band structure and phonon dispersion, the main emphasis is on describing relevant experiments and important results as well as some of the novel applications of graphene. In particular, this review covers graphene synthesis and characterization, field-effect behavior, electronic transport properties, magnetotransport, integer and fractional quantum Hall effects, mechanical properties, transistors, optoelectronics, graphene-based sensors, and biosensors. This approach attempts to highlight both the means by which the current understanding of graphene has come about and some tools for future contributions.

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13

BERG, A., D. WEISS, K. V. KLITZING, and R. NÖTZEL. "SPIN SPLITTING IN A TWO DIMENSIONAL ELECTRON SYSTEM DETERMINED BY NUCLEAR MAGNETIC RELAXATION AND MAGNETOTRANSPORT ACTIVATION MEASUREMENTS." International Journal of Modern Physics B 07, no. 01n03 (January 1993): 474–79. http://dx.doi.org/10.1142/s0217979293000998.

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The spin splitting observed in two-dimensional electron systems at high magnetic fields is not only determined by the single-electron Zeeman energy but also by many-particle effects. Electron-electron interaction results in an enhanced g-factor which can be described by the exchange part of the Coulomb interaction. Nuclear spin lattice relaxation experiments analysing the Overhauser Shift in Electron Spin Resonance (ESR) measurements reveal that the exchange term is dominant. The spin splitting is strongly dependent on magnetic field and temperature. Numerical simulations enable the quantitative determination of the exchange part of the spin split energy. Transport activation measurements verify that the exchange part is proportional to the spin polarization of the electrons.

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14

WEXLER, CARLOS, and ORION CIFTJA. "NOVEL LIQUID CRYSTALLINE PHASES IN QUANTUM HALL SYSTEMS." International Journal of Modern Physics B 20, no. 07 (March 20, 2006): 747–78. http://dx.doi.org/10.1142/s0217979206033632.

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Since 1999, experiments have shown a plethora of surprising results in the low-temperature magnetotransport in intermediate regions between quantum Hall (QH) plateaus: the extreme anisotropies observed for half-filling, or the re-entrant integer QH effects at quarter filling of high Landau levels (LL); or even an apparent melting of a Wigner Crystal (WC) at filling factor ν = 1/7 of the lowest LL. A large body of seemingly distinct experimental evidence has been successfully interpreted in terms of liquid crystalline phases in the two-dimensional electron system (2DES). In this paper, we present a review of the physics of liquid crystalline states for strongly correlated two-dimensional electronic systems in the QH regime. We describe a semi-quantitative theory for the formation of QH smectics (stripes), their zero-temperature melting onto nematic phases and ultimate anisotropic-isotropic transition via the Kosterlitz–Thouless (KT) mechanism. We also describe theories for QH-like states with various liquid crystalline orders and their excitation spectrum. We argue that resulting picture of liquid crystalline states in partially filled LL-s is a valuable starting point to understand the present experimental findings, and to suggest new experiments that will lead to further elucidation of this intriguing system.

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15

Złotnik, Sebastian, Jarosław Wróbel, Jacek Boguski, Małgorzata Nyga, Marek Andrzej Kojdecki, and Jerzy Wróbel. "Facile and Electrically Reliable Electroplated Gold Contacts to p-Type InAsSb Bulk-Like Epilayers." Sensors 21, no. 16 (August 4, 2021): 5272. http://dx.doi.org/10.3390/s21165272.

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Narrow band-gap semiconductors, namely ternary InAsSb alloys, find substantial technological importance for mid-infrared application as photodetectors in medical diagnostics or environmental monitoring. Thus, it is crucial to develop electrical contacts for these materials because they are the fundamental blocks of all semiconductor devices. This study demonstrates that electroplated gold contacts can be considered as a simple and reliable metallization technology for the electrical-response examination of a test structure. Unalloyed electroplated Au contacts to InAsSb exhibit specific contact resistivity even lower than vacuum-deposited standard Ti–Au. Moreover, temperature-dependent transport properties, such as Hall carrier concentration and mobility, show similar trends, with a minor shift in the transition temperature. It can be associated with a difference in metallization technology, mainly the presence of a Ti interlayer in vacuum-deposited contacts. Such a transition may give insight into not only the gentle balance changes between conductivity channels but also an impression of changing the dominance of carrier type from p- to n-type. The magnetotransport experiments assisted with mobility spectrum analysis clearly show that such an interpretation is incorrect. InAsSb layers are strongly p-type dominant, with a clear contribution from valence band carriers observed at the whole analyzed temperature range. Furthermore, the presence of thermally activated band electrons is detected at temperatures higher than 220 K.

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Chun, S. H., M. B. Salamon, Y. Lyanda-Geller, P. M. Goldbart, and P. D. Han. "Magnetotransport in Manganites and the Role of Quantal Phases: Theory and Experiment." Physical Review Letters 84, no. 4 (January 24, 2000): 757–60. http://dx.doi.org/10.1103/physrevlett.84.757.

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17

Dorozhkin, S. I., C. J. Emeleus, O. A. Mironov, T. E. Whall, and G. Landwehr. "Magnetotransport anomalies in dilute two-dimensional electron systems: an experiment and a model." Surface Science 361-362 (July 1996): 933–36. http://dx.doi.org/10.1016/0039-6028(96)00568-7.

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18

Bansal, Bhavtosh, V. K. Dixit, V. Venkataraman, and H. L. Bhat. "Transport, optical and magnetotransport properties of hetero-epitaxial InAsxSb1−x/GaAs(x⩽0.06) and bulk crystals: experiment and theoretical analysis." Physica E: Low-dimensional Systems and Nanostructures 20, no. 3-4 (January 2004): 272–77. http://dx.doi.org/10.1016/j.physe.2003.08.017.

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19

PATANÈ, A. "NEGATIVE DIFFERENTIAL VELOCITY IN ARTIFICIAL CRYSTALS PROBED BY HIGH MAGNETIC FIELDS." International Journal of Modern Physics B 23, no. 12n13 (May 20, 2009): 2766–68. http://dx.doi.org/10.1142/s0217979209062335.

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Progress in the synthesis and engineering of semiconductor materials has led to improved device performances and functionalities. In particular, in the last decade, there has been considerable interest in the physics and applications of highly-mismatched alloys in which small and highly-electronegative isovalent N -atoms are incorporated onto the anion sublattice of a III-V compound semiconductor.1 The most studied material is the GaAs 1-x N x alloy. Our magnetotunnelling studies have shown that a small percentage of N (x < 1%) perturbs dramatically the electronic properties of the host GaAs crystal leading to a large increase of the electron effective mass and an unusual response of the energy-wavevector dispersions to hydrostatic pressure.2–6 These effects differ from the smoother variation of the energy band gap and electron effective mass with alloy composition observed in other semiconductor compounds, such as In y Ga 1-y As . The incorporation of N in GaAs gives rise to a qualitatively different type of alloy phenomenon: N -impurities and N -clusters tend to localize the extended Bloch states of GaAs at resonant energies in the conduction band (CB), thus fragmenting the energy-wavevector dispersion relations. The possibility of tailoring the electronic properties of III-V compounds by N -incorporation has stimulated proposals for innovative devices in optoelectronics and high frequency (terahertz, THz) electronics.7 However, to date, the implementation of dilute nitrides in these technologies presents several challenges, including a degradation of the electron mobility. Also, despite a rapidly expanding body of work on the electronic properties of GaAs 1-x N x, the range of N -concentrations over which this alloy behaves as a good conductor is not yet well established. Our magnetotransport experiments have revealed how the incorporation of N in GaAs affects the electrical conductivity. Our studies in n-type GaAs 1-x N x epilayers revealed a large increase of the resistivity, ρ, for x > 0.2%, which we have attributed to the emergence of defect states with deep (~ 0.3 eV) energy levels. Electron trapping onto these states was not observed at low x (x = 0.2%). In this ultra-dilute alloy regime and at low electric fields (F < 1 kV / cm ) the electrical conductivity retains the characteristic features of transport through extended states, albeit with relatively low mobility (µ ~ 0.1 m 2/ Vs at RT) due to scattering of electrons by N -atoms. We have focused our research on this ultra-dilute regime and exploited the admixing of the localized single N -impurity level with the extended conduction band states of GaAs to realize an unusual type of negative differential velocity (NDV) effect: at large F (> 1 kV / cm ), electrons gain sufficient energy to approach the energy of the resonant N -level, where they become spatially localized.7–10 [Formula: see text] This Resonant Electron Localization in Electric Field, to which we give the acronym RELIEF, leads to NDV and strongly non-linear current-voltage characteristics. We envisage that the RELIEF-effect could be observed in other III-N-V alloys, such as InP 1-x N x and InAs 1-x N x. In these compounds the nature of the resonant interaction between the N -level and the conduction band states of the host-crystal is still relatively unexplored. However, it is clear that the different energy positions of the N -level relative to the conduction band minimum of different materials could offer new degrees of freedom in the design of the electronic band structure and electron dynamics. The RELIEF-effect may open up prospects for future applications in fast electronics. We have shown that the maximum response frequency, fmax, of a RELIEF-diode can be tuned by the applied electric field in the THz frequency range.7 This is of potential technological significance for the development of detectors/sources in the 0.6-1 THz region, which is not currently attainable using conventional Transferred Electron Devices and Quantum Cascade Lasers. Our recent studies of GaAs 1-x N x have also shown a fast response of the current in the sub-THz frequency range.11 Experiments involving diodes optimized for THz-operation coupled with a quantitative theoretical model of the THz dynamics will be now needed to assess the use of GaAs 1-x N x and other III-N-V alloys in detectors/sources of THz radiation. Note from Publisher: This article contains the abstract only.

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20

Paolucci, Federico, Giorgio De Simoni, Paolo Solinas, Elia Strambini, Nadia Ligato, Pauli Virtanen, Alessandro Braggio, and Francesco Giazotto. "Magnetotransport Experiments on Fully Metallic Superconducting Dayem-Bridge Field-Effect Transistors." Physical Review Applied 11, no. 2 (February 25, 2019). http://dx.doi.org/10.1103/physrevapplied.11.024061.

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21

Teubert, J., P. J. Klar, A. Lindsay, and E. P. O’Reilly. "Evidence of localized boron impurity states in (B,Ga,In)As in magnetotransport experiments under hydrostatic pressure." Physical Review B 83, no. 3 (January 13, 2011). http://dx.doi.org/10.1103/physrevb.83.035203.

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22

Zou, W., X. W. Zhou, J. J. Quan, Y. G. Yang, H. N. G. Wadley, D. Brownell, D. Wang, et al. "Sputter Deposition of GMR Spin Valves." MRS Proceedings 616 (2000). http://dx.doi.org/10.1557/proc-616-135.

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AbstractRadio frequency (RF) diode sputtering has been used for the growth of giant magnetoresistive (GMR) metal multilayers. Control of the atomic-scale structure of the surfaces and interfaces within these films is critical for GMR applications. A systematic series of experiments have been conducted to evaluate the dependence of the magnetotransport properties upon the growth conditions (i.e. background pressure, input power) for NiFeCo/CoFe/CuAgAu spin valves during RF diode sputter deposition. By using computational fluid dynamics, plasma, molecular dynamics, and various Monte Carlo techniques, a multiscale modeling approach has investigated the atomic assembly events during film growth. Energetic metal atoms and inert gas ion fluxes are shown to have very strong effects upon interfacial structures. The insights gained have led to novel deposition strategy propopositions for interface morphology control.

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23

Fontcuberta, J., M. Bibes, M. Wojcik, E. Jedryka, S. Nadolski, S. València, Ll Balcells, and B. Martínez. "Phase Separation at Interfaces in La2/3Ca1/3MnO3 Thin Films." MRS Proceedings 690 (2001). http://dx.doi.org/10.1557/proc-690-f4.1.

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ABSTRACTWe present an extensive physical characterization of La2/3Ca1/3MnO3 (LCMO) epitaxial films grown on SrTiO3 (STO), LaAlO3 (LAO) and NdGaO3 (NGO) substrates. The main difference among these substrates is that they have a different mismatch (∼ 1.2%, -1.8% and - 0.1%, respectively) with the manganite. The films can be coherently grown up to 180 nm for STO and NGO but partial relaxation is observed for LAO. The magnetotransport data indicate that very thin films (<27nm) display non-conventional magnetoresistive properties: a substantial magnetoresistance develops which can be progressively appreciated for STO and LAO films. 55Mn-Nuclear Magnetic Resonance experiments on all these films reveal the presence of non-homogeneous electronic states. These experiments in fact provide clear evidence of the presence of two distinguishable ferromagnetic Mn states and a non-ferromagnetic phase. The possible role of strain-induced charge localization is discussed. It turns out that electronic phase separation occurs in all films irrespectively of the particular substrate used; thus we conclude that strain is not the unique driving force for charge localization.

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Knap, W., E. Borovitskaya, M. S. Shur, R. Gaska, G. Karczewski, B. Brandt, D. Maude, et al. "High Magnetic Field Studies of AlGaN/GaN Heterostructures Grown on Bulk GaN, SiC, and Sapphire Substrates." MRS Proceedings 639 (2000). http://dx.doi.org/10.1557/proc-639-g7.3.

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ABSTRACTWe present the results of the high magnetic field studies of properties of two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures grown over high-pressure bulk GaN, sapphire, and insulating SiC substrates. The experimental results include the low field Hall measurements, cyclotron resonance measurements, and cryogenic temperature Quantum Hall Effect studies as well as room-temperature characteristics of High Electron Mobility Transistors fabricated on all these substrates. The room temperature high field measurements allow us to clearly separate the contributions of a parasitic parallel conduction from 2DEG conduction in all investigated heterostructures.The magnetotransport measurements are performed in the magnetic fields up to 30 Tesla for temperatures between 50mK-300K. This high magnetic field in combination with very high mobilities (over 60.000 cm2/Vs) in the sample on the bulk GaN substrates allow us to observe features related both to cyclotron resonance and spin splitting. The temperature dependence of this splitting determines the spin and cyclotron resonance energy gaps and, in combination with cyclotron resonance and tilted field experiments, allows us to determine the complete energy structure of 2DEG conduction band. We also present the first experimental results showing so called “the exchange enhancement” of the energy gaps between spin Landau levels.

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25

Zou, W., H. N. G. Wadley, X. W. Zhou, R. A. Johnson, and D. Brownell. "Composition-Morphology-Property Relations For Giant Magnetoresistance Multilayers Grown By RF Diode Sputtering." MRS Proceedings 674 (2001). http://dx.doi.org/10.1557/proc-674-t1.5.

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ABSTRACTA series of experiments have been conducted to evaluate the magnetotransport properties of RF diode sputter deposited giant magnetoresistive (GMR) multilayers with either copper or copper-silver-gold nonferromagnetic (NFM) conducting layers. The study revealed that RF diode deposited multilayers utilizing Cu80Ag15Au5 as the NFM conducting layer posses significantly superior giant magnetoresistance to otherwise identical device architectures that used pure copper as the NFM conducting layer. To explore the origin of this effect, copper and Cu80Ag15Au5 films of varying thickness have been grown under identical deposition conditions and their surface morphology and roughness investigated. Atomic force microscopy revealed significant roughness and the presence of many pinholes in thin pure copper films. The surface roughness of the Cu80Ag15Au5 layers was found to be much less than that of pure copper, and the alloying eliminated the formation of pinholes. Molecular statics estimates of activation barriers indicated that both silver and gold have significantly higher mobilities than copper atoms on a flat copper surface. However, gold is found to be incorporated in the lattice whereas silver tends to segregate (and concentrate) upon the free surface, enhancing its potency as a surfactant. The atomic scale mechanism responsible for silver's surface flattening effect has been explored.

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"Anomalous Hall effect and magnetotransport effects in the organic superconductor (TMTSF ) 2 CIO 4." Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 314, no. 1528 (May 30, 1985): 97–103. http://dx.doi.org/10.1098/rsta.1985.0010.

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The organic conductor (TMTSF) 2 CIO 4 exhibits unusual magnetotransport effects below 30 K. The resistivity and thermopower have large, anisotropic changes in a magnetic field, whereas the thermal conductivity is hardly affected. At lower temperature ( T ≤ 5 K) a magnetic field applied along the c * direction causes a phase transition from a metallic, non-magnetic state to a semimetallic, magnetic state. This orbitally induced transition appears to be unique in nature. Above the threshold field for this transition steps in the Hall resistance are observed, suggestive of the quantum Hall effect. In this paper we review the magnetotransport experiment in these materials and discuss the possible origins of the unusual phenomena observed.

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Journal articles on the topic 'Magnetotransport experiments'

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