WEAK LOCALIZATION AND ITS APPLICATIONS AS AN EXPERIMENTAL TOOL

2010 ◽  
Vol 24 (12n13) ◽  
pp. 2015-2052 ◽  
Author(s):  
Gerd Bergmann
Keyword(s):  
Magnetic Moments ◽  
Weak Localization ◽  
Electron System ◽  
Spin Fluctuations ◽  
Magnetic Impurities ◽  
Electron Systems ◽  
Magnetic Systems ◽  
Disordered Films ◽  
Liquid Behavior ◽  
Important Field

The resistance of two-dimensional electron systems such as thin disordered films shows deviations from Boltzmann theory, which are caused by quantum corrections and are called weak localization. The theoretical origin of weak localization is the Langer–Neal graph in Kubo formalism. It represents an interference experiment with conduction electrons split into pairs of waves interfering in the back-scattering direction. The intensity of the interference (integrated over the time) can easily be measured by the resistance of the film. The application of a magnetic field B destroys the phase coherence after a time which is proportional to 1/B. For a field of 1 T this time is of the order of 1 ps. Therefore with a dc experiment, one can measure characteristic times of the electron system in the range of picoseconds. Weak localization has been applied to measure dephasing, spin-orbit scattering, tunneling times, etc. One important field of application is the investigation of magnetic systems and magnetic impurities by measuring the magnetic dephasing time and its temperature dependence. Here the Kondo maximum of spin-flip scattering, spin-fluctuations, Fermi liquid behavior and magnetic d-resonances have been investigated. Another field is the detection of magnetic moments for very dilute alloys and surface impurities. This article given a brief survey of different applications of weak localization with a focus on magnetic impurities.

QUANTUM CRITICAL FLUCTUATIONS IN HEAVY FERMION COMPOUNDS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3031-3036 ◽  
Author(s):  
A. SCHROEDER ◽  
G. AEPPLI ◽  
P. COLEMAN ◽  
R. RAMAZASHVILI ◽  
R. COLDEA ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Heavy Fermion ◽  
Magnetic Moments ◽  
Quantum Critical Point ◽  
Electron System ◽  
Spin Fluctuations ◽  
Scattering Data ◽  
Critical Fluctuations ◽  
Conventional View ◽  
Quantum Critical

The electronic properties of heavy fermion alloys are dominated by spin fluctuations which are expected to become critical when tuned by pressure to a quantum critical point (QCP), entering a magnetic ordered state. Apart from the onset of exotic superconductivity, unexpected "normal conducting" behavior is found close to the QCP, which does not seem only to escape the conventional view of metals (Fermi liquids) but also the "conventional view" of an antiferromagnetic quantum phase transition in these f-metals. So far only few compounds have been investigated by neutron scattering to directly reveal the critical fluctuations spectrum. In CeCu 59 Au 01 the fluctuations develop an unusual energy dependence, characterized by an exponent α = 0.75, which persist over the entire Brillouin zone, provoking an unexpected local non Fermi liquid behavior. The same unusual exponent derived from E/T scaling determines the H/T scaling of the uniform magnetization. Recent neutron scattering data in magnetic fields further confirm this picture of nearly free local magnetic moments (modified by α) emerging at the antiferromagnetic QCP in this strongly correlated electron system.

Mobility of Charge Carriers in Dilute Magnetic Semiconductors

2007 ◽  
Vol 999 ◽  
Author(s):  
Michael G. Foygel ◽  
James Niggemann ◽  
A. G. Petukhov
Keyword(s):  
Magnetic Field ◽  
Electrical Transport ◽  
Magnetic Semiconductors ◽  
Magnetic Moments ◽  
Dilute Magnetic Semiconductors ◽  
Charge Carriers ◽  
Spin Fluctuations ◽  
Magnetic Impurities ◽  
Mobility Of Charge Carriers ◽  
The Magnetic Field

AbstractWe studied electrical transport in dilute magnetic semiconductors, which is determined by scattering of free carriers by localized magnetic moments. In our calculations of the scattering time and the mobility of the majority and minority-spin carriers we took into account both the effects of thermal spin fluctuations and of built-in spatial disorder of the magnetic atoms. These effects are responsible for the magnetic-field dependence of the mobility of the charge carriers. The application of the external magnetic field suppresses the thermodynamic spin fluctuations thus increasing the mobility. Simultaneously, depending on the type of the carriers and on parameters of the impurity potential, scattering by built-in spatial fluctuations of the atomic spins increases or decreases with the magnetic field. The latter effect is due to the change in the magnitude of the random local Zeeman splitting with the magnetic field. We discuss the role of the above effects on mobility and magnetoresistance of semiconductors where magnetic impurities are electrically active or neutral.

scholarly journals Irradiation-induced Kondo resonance in two-dimensional electron systems

2021 ◽  
Vol 2015 (1) ◽  
pp. 012056
Author(s):  
I. V. Iorsh ◽  
O. V. Kibis
Keyword(s):  
Quantum Wells ◽  
State Of The Art ◽  
Magnetic Moments ◽  
Resonant Scattering ◽  
Electron System ◽  
Kondo Temperature ◽  
Two Dimensional ◽  
Electron Systems ◽  
Kondo Resonance ◽  
Scattering States

Abstract We demonstrated theoretically that formation of the resonant scattering states in the two-dimensional (2D) electron system irradiated by a circularly polarized electromagnetic field leads to the emergence of localized magnetic moments. As a consequence, the corresponding Kondo resonances appear. For GaAs-based quantum wells and microwave fields, we estimate the Kondo temperature around 2.5 K, which can be detected in state-of-the-art measurements.

scholarly journals Non-Fermi-Liquid Behavior in Metallic Quasicrystals with Local Magnetic Moments

2015 ◽  
Vol 115 (3) ◽  
Author(s):  
Eric C. Andrade ◽  
Anuradha Jagannathan ◽  
Eduardo Miranda ◽  
Matthias Vojta ◽  
Vladimir Dobrosavljević
Keyword(s):  
Fermi Liquid ◽  
Magnetic Moments ◽  
Liquid Behavior ◽  
Fermi Liquid Behavior

scholarly journals Non-Fermi-liquid behavior and spin fluctuations in dopedUAl2

1997 ◽  
Vol 55 (2) ◽  
pp. 947-953 ◽  
Author(s):  
F. Mayr ◽  
G.-F. v. Blanckenhagen ◽  
G. R. Stewart
Keyword(s):  
Fermi Liquid ◽  
Spin Fluctuations ◽  
Liquid Behavior ◽  
Fermi Liquid Behavior

Magnetism, spin fluctuations, and non-Fermi-liquid behavior in(UxLa1−x)2Zn17

2001 ◽  
Vol 64 (6) ◽  
Author(s):  
G.-F. von Blanckenhagen ◽  
E.-W. Scheidt ◽  
T. Schreiner ◽  
G. R. Stewart
Keyword(s):  
Fermi Liquid ◽  
Spin Fluctuations ◽  
Liquid Behavior ◽  
Fermi Liquid Behavior

The Dependence of Magnetic Moments on Magnetic Impurities of Ni in Eu1.86Ce0.14Cu1-yNiyO4+a-d

2020 ◽  
Vol 860 ◽  
pp. 148-153
Author(s):  
Muhammad Abdan Syakuur ◽  
Yati Maryati ◽  
Utami Widyaiswari ◽  
Dita Puspita Sari ◽  
Togar Saragi ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Low Temperatures ◽  
Unit Volume ◽  
Magnetic Impurity ◽  
Magnetic Moments ◽  
Magnetic Impurities ◽  
Superconducting Cuprates ◽  
Susceptibility Data ◽  
Diamagnetic Behavior ◽  
Volume Unit

The partially substitution of magnetic impurity Ni for Cu in electron-doped superconducting cuprates of Eu2-xCexCu1-yNiyO4+a-d with x = 0.14 and y = 0, 0.01 and 0.02 has been studied in order to investigate the effect of Ni impurity on structure and the value of magnetic moments per unit volume extracted from susceptibility data in under-doped region. Magnetic-susceptibility measurements were carried out at low temperatures down to 2 K. For sample with y = 0, diamagnetic behavior is observed starting from about 9 K. The superconductivity disappeared at y ³ 0.01. The values of magnetic moment in every volume unit decreased with increasing Ni.

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