Bound magnetic polaron hopping and giant magnetoresistance in magnetic semiconductors and nanostructures

2000 ◽  
Vol 62 (1) ◽  
pp. 520-531 ◽  
Author(s):  
A. G. Petukhov ◽  
M. Foygel
Keyword(s):  
Giant Magnetoresistance ◽  
Magnetic Semiconductors ◽  
Magnetic Polaron ◽  
Polaron Hopping ◽  
Bound Magnetic Polaron

Variable-Range Hopping in the Array of Magnetic Quantum Dots

2001 ◽  
Vol 690 ◽  
Author(s):  
M. Foygel ◽  
R. D. Morris ◽  
A. G. Petukhov
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Low Temperatures ◽  
Giant Magnetoresistance ◽  
Magnetic Semiconductors ◽  
Magnetic Polaron ◽  
Variable Range Hopping ◽  
Bound Magnetic Polaron ◽  
Variable Range ◽  
Magnetic Quantum Dots

ABSTRACTWe analyzed the spin-dependent conductivity in the system of paramagnetic quantum dots embedded in semi-insulating matrix, which is due to bound magnetic polaron (BMP) inter-dot hopping. If such a system is characterized by wide distributions of the “bare” electron energies and BMP shifts, variable-range and variable-polaron-barrier hopping can be observed at low temperaturesT. It results in the giant magnetoresistance,ρ(H, T ) governed by a non-activation law, lnρ /α [T0(H)/T ]p, whereT0(H) drops with magnetic field,H. Depending on the conditions, parameters of the material, and the dimensionality of the system, the exponent 0.25 < p < 0.75. This type ofT -dependence has been observed in GaMnAs and MnGe magnetic semiconductors.

Bound magnetic polaron in magnetic semiconductors

1979 ◽  
Vol 94 (1) ◽  
pp. 181-190 ◽  
Author(s):  
P. Kuivalainen ◽  
J. Sinkkonen ◽  
K. Kaski ◽  
T. Stubb
Keyword(s):  
Magnetic Semiconductors ◽  
Magnetic Polaron ◽  
Bound Magnetic Polaron

Photoluminescence Studies of Diluted Magnetic Semiconductors Under Hydrostatic Pressure: Cd1−xMnxTe

1989 ◽  
Vol 161 ◽  
Author(s):  
Maneesha Prakash ◽  
Meera Chandrasekhar ◽  
H.R. Chandrasekhar ◽  
I. Miotkowski ◽  
A.K. Ramdas
Keyword(s):  
Hydrostatic Pressure ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Binding Energies ◽  
Magnetic Polaron ◽  
Photoluminescence Study ◽  
Bound Magnetic Polaron ◽  
Pressure Coefficients ◽  
Diluted Magnetic ◽  
Photoluminescence Studies

ABSTRACTWe present a photoluminescence study of the excitons and electron-to-acceptor (e-°) transitions in Cd1−xMnxTe (x = 0.05 and 0.15) under hydrostatic pressure at 15K. We investigate the changing magnetic and Coulombic binding energies of the e-° transition under pressure. We find that the e-° binding energy increases with pressure for x = 0.15 where the magnetic term due to the acceptor bound magnetic polaron is large, while it decreases for x = 0.05. We also obtain the pressure coefficients of the excitonic and acceptor related transitions.

Spin-Texture in Acceptor-Bound Magnetic Polarons

1986 ◽  
Vol 89 ◽  
Author(s):  
Eric D. Isaacs ◽  
Peter A. Wolff
Keyword(s):  
Neutron Scattering ◽  
Valence Band ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Magnetic Polaron ◽  
Spin Orbit ◽  
Bound Magnetic Polaron ◽  
Magnetic Polarons ◽  
Diluted Magnetic ◽  
Spin Texture

AbstractWe outline a theory of the acceptor-bound magnetic polaron in cubic diluted magnetic semiconductors that exhibits a nonuniform magnetization. Calculations show that the manganese spins have an overall z-alignment, but are canted in an azimuthally symmetric way from that direction. This is new phenomenon we call BMP spin-texture. Spin-texture results from valence band degeneracy, and the important spin-orbit effects associated with it. The possibility of studying BMP spin-texture via neutron scattering is discussed.

Bound magnetic polaron in Cr-based diluted magnetic semiconductors

1998 ◽  
Vol 58 (11) ◽  
pp. 7024-7034 ◽  
Author(s):  
M. Herbich ◽  
A. Twardowski ◽  
D. Scalbert ◽  
A. Petrou
Keyword(s):  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Magnetic Polaron ◽  
Bound Magnetic Polaron ◽  
Diluted Magnetic

What Limits Magnetic Polaron Energies in DMS?

1986 ◽  
Vol 89 ◽  
Author(s):  
P. A. Wolff ◽  
L. R. Ram-Mohan
Keyword(s):  
Optical Properties ◽  
Exchange Interaction ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Exchange Potential ◽  
Magnetic Polaron ◽  
Bound Magnetic Polaron ◽  
Magnetic Polarons ◽  
Spin Clusters ◽  
Diluted Magnetic

Magnetic polarons are ferromagnetic spin clusters created by the exchange interaction of a carrier spin (electron or hole) with localized spins imbedded in a semiconductor lattice. They were first studied in magnetic semiconductors [1]; more recently, there have been extensive investigations [2] of polaron behavior in diluted magnetic semiconductors (DMS), such as Cd1−xMnxTe. DMS are favorable media for magnetic polaron studies because they have simple s-p bands and excellent optical properties. Two types of magnetic polarons have been identified in DMS - the bound magnetic polaron (BMP), whose carrier is localized by an impurity [3], and the free polaron (FP) consisting of a carrier trapped by its own, self-consistently-maintained, exchange potential [4].

Colossal Hopping Magnetoresistance of GaAs/ErAs Nanocomposites

1999 ◽  
Vol 581 ◽  
Author(s):  
A. G. Petukhov ◽  
M. Foygel ◽  
A. Chantis
Keyword(s):  
Giant Magnetoresistance ◽  
Magnetic Semiconductors ◽  
Dilute Magnetic Semiconductors ◽  
Golden Rule ◽  
Magnetic Polaron ◽  
Local Magnetization ◽  
Ginzburg Landau ◽  
Site Model ◽  
Rule Approach ◽  
Low Magnetic Field

ABSTRACTA theory of bound magnetic polaron (BMP) hopping, driven by thermodynamic fluctuations of the local magnetization, has been developed. It is based on a two-site model of BMP's. The BMP hopping probability rate was calculated in the framework of the “Golden Rule” approach by using the Ginzburg-Landau effective Hamiltonian method. The theory explains the main features of hopping resistivity observed in a variety of experiments in dilute magnetic semiconductors and magnetic nanocomposites, namely: (a) negative giant magnetoresistance, the scale of which is governed by a magnetic polaron localization volume, and (b) low magnetic field positive magnetoresistance, which usually preceeds negative magnetoresistance.

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