Search results for "Hall effect"
showing 10 items of 702 documents
InAs/InP single quantum wire formation and emission at 1.5 microns
2006
Isolated InAs/InP self-assembled quantum wires have been grown using in situ accumulated stress measurements to adjust the optimal InAs thickness. Atomic force microscopy imaging shows highly asymmetric nanostructures with average length exceeding more than ten times their width. High resolution optical investigation of as-grown samples reveals strong photoluminescence from individual quantum wires at 1.5 microns. Additional sharp features are related to monolayer fluctuations of the two dimensional InAs layer present during the early stages of the quantum wire self-assembling process.
Writing and reading antiferromagnetic Mn
2017
Using antiferromagnets as active elements in spintronics requires the ability to manipulate and read-out the Néel vector orientation. Here we demonstrate for Mn2Au, a good conductor with a high ordering temperature suitable for applications, reproducible switching using current pulse generated bulk spin-orbit torques and read-out by magnetoresistance measurements. Reversible and consistent changes of the longitudinal resistance and planar Hall voltage of star-patterned epitaxial Mn2Au(001) thin films were generated by pulse current densities of ≃107 A/cm2. The symmetry of the torques agrees with theoretical predictions and a large read-out magnetoresistance effect of more than ≃6% is reprod…
Диссипативное туннелирование электронов в вертикально связанных двойных асимметричных квантовых точках InAs/GaAs(001)
2021
We report on the results of experimental studies of the photoelectric properties of a GaAs p-i-n photodiode with InAs/GaAs(001) double asymmetric quantum dots (DAQDs) grown by self-assembling in Metal Organic Vapor Phase Epitaxy (MOVPE) process. Three peaks were observed in the dependence of the photocurrent on the reverse bias measured at monochromatic photoexcitation of the DAQDs at the wavelength corresponding to the energy of interband optical transitions between the ground hole and electron states in the bigger QDs. These peaks were related to the tunneling of the photoexcited electrons between the QDs including the dissipative one (with emission and absorption of the optical phonons)…
Giant Negative Magnetoresistance Driven by Spin-Orbit Coupling at the LaAlO3/SrTiO3 Interface
2015
The LaAlO3/SrTiO3 interface hosts a two-dimensional electron system that is unusually sensitive to the application of an in-plane magnetic field. Low-temperature experiments have revealed a giant negative magnetoresistance (dropping by 70%), attributed to a magnetic-field induced transition between interacting phases of conduction electrons with Kondo-screened magnetic impurities. Here we report on experiments over a broad temperature range, showing the persistence of the magnetoresistance up to the 20 K range--indicative of a single-particle mechanism. Motivated by a striking correspondence between the temperature and carrier density dependence of our magnetoresistance measurements we prop…
Exciton recombination dynamics in InAs∕InP self-assembled quantum wires
2005
In this work we investigate the exciton recombination dynamics in InAs∕InP semiconductor self-assembled quantum wires, by means of continuous wave and time resolved photoluminescence. The continuous wave photoluminescence results seem to indicate that the temperature quenching of the emission band seems to be more probably due to unipolar thermal escape of electrons towards the InP barrier. On the other hand, the analysis of time resolved photoluminescence reveals that the temperature dependence of the radiative and nonradiative recombination times is mainly determined by the dynamics of excitons localized by disorder (high energy tail of the PL band) and strongly localized (low energy tail…
Photoluminescence from strained InAs monolayers in GaAs under pressure
1994
bulk GaAs. At pressures above the band crossover two emission bands are observed. These bands, characterized by having negative pressure coefBcients, are attributed to the type-I transition between conduction-band X „and heavy-hole states of the InAs monolayer and the type-II transition &om X states in GaAs to InAs heavy-hole states. The results are interpreted in terms of tight-binding band-structure calculations for the strained InAs-monolayer — bulk-GaAs system. I. INTRODUCTION Highly strained InAs jGaAs heterostructures have recently attracted interest due to their unusual electronic and optical properties. ~ 4 Epitaxial isomorphic growth of InAs on GaAs can be achieved only up to a sma…
Transport Properties of Co2(Mn, Fe)Si Thin Films
2013
Thin Heusler films with the composition Co2Mn1−x Fe x Si were grown by both sputter and pulsed laser deposition. The samples show a high degree of structural order and very good magnetic properties. The availability of thin film samples on dielectric substrates allowed the systematic investigation of their electronic properties by transport experiments. The normal Hall effect shows a transition from a hole-like charge transport in Co2MnSi to an electron-like transport in Co2FeSi. This is in agreement with calculations, which predict that the substitution of Mn by Fe leads to a band filling and a shift of the Fermi energy. Furthermore, the behavior of the anomalous Hall effect was studied. I…
Epitaxy and magnetotransport ofSr2FeMoO6thin films
2000
By pulsed-laser deposition epitaxial thin films of ${\mathrm{Sr}}_{2}{\mathrm{FeMoO}}_{6}$ have been prepared on (100) ${\mathrm{SrTiO}}_{3}$ substrates. Already for a deposition temperature of 320 \ifmmode^\circ\else\textdegree\fi{}C epitaxial growth is achieved. Depending on deposition parameters the films show metallic or semiconducting behavior. At high (low) deposition temperature the FeMo sublattice has a rock-salt (random) structure. The metallic samples have a large negative magnetoresistance which peaks at the Curie temperature. The magnetic moment was determined to $4{\ensuremath{\mu}}_{B}$ per formula unit (f.u.), in agreement with the expected value for an ideal ferrimagnetic ar…
Giant and Tunneling Magnetoresistance in Unconventional Collinear Antiferromagnets with Nonrelativistic Spin-Momentum Coupling
2022
Giant and tunneling magnetoresistance are physical phenomena used for reading information in commercial spintronic devices. The effects rely on a conserved spin current passing between a reference and a sensing ferromagnetic electrode in a multilayer structure. Recently, we have proposed that these fundamental spintronic effects can be realized in unconventional collinear antiferromagnets with nonrelativistic alternating spin-momentum coupling. Here, we elaborate on the proposal by presenting archetype model mechanisms for the giant and tunneling magnetoresistance effects in multilayers composed of these unconventional collinear antiferromagnets. The models are based, respectively, on aniso…
WS2/MoS2 Heterostructures through Thermal Treatment of MoS2 Layers Electrostatically Functionalized with W3S4 Molecular Clusters
2020
The preparation of 2D stacked layers that combine flakes of different nature, gives rise to countless number of heterostructures where new band alignments, defined at the interfaces, control the electronic properties of the system. Among the large family of 2D/2D heterostructures, the one formed by the combination of the most common semiconducting transition metal dichalcogenides WS2/MoS2, has awaken great interest due to its photovoltaic and photoelectrochemical properties. Solution as well as dry physical methods have been developed to optimize the synthesis of these heterostructures. Here a suspension of negatively charged MoS2 flakes is mixed with a methanolic solution of a cationic W3S…