Effect of thermodynamic fluctuations of magnetization on the bound magnetic polaron in dilute magnetic semiconductors

1983 ◽  
Vol 28 (3) ◽  
pp. 1548-1563 ◽  
Author(s):  
T. Dietl ◽  
J. Spałek
Keyword(s):  
Magnetic Semiconductors ◽  
Dilute Magnetic Semiconductors ◽  
Magnetic Polaron ◽  
Bound Magnetic Polaron

ANISOTROPY OF THE BOUND MAGNETIC POLARON STATES AND COLOSSAL HOPPIG MAGNETORESISTANCE IN DILUTE MAGNETIC SEMICONDUCTORS

2001 ◽  
Vol 15 (24n25) ◽  
pp. 3228-3237 ◽  
Author(s):  
M. Foygel ◽  
A. G. Petukhov
Keyword(s):  
Colossal Magnetoresistance ◽  
Magnetic Semiconductors ◽  
Dilute Magnetic Semiconductors ◽  
Magnetic Polaron ◽  
Local Magnetization ◽  
Ginzburg Landau ◽  
Local Exchange ◽  
Bound Magnetic Polaron ◽  
Trapped Electron ◽  
The Magnetic Field

A theory of positive and negative colossal magnetoresistance (CMR) in dilute magnetic semiconductors (DMS) is presented. The phenomenon is described in the framework of bound magnetic polaron (BMP) hopping, driven by thermodynamic fluctuations of the local magnetization. The latter is caused by fluctuating spins of the magnetic atoms which strongly interact with the spin of a trapped electron or a hole within the localization volume. The authors' previous approach to the BMP hopping problem1,2, based on the Ginzburg-Landau effective Hamiltonian method, has been generalized in order to take into account the anisotropy of the BMP states. This effect can be attributed to the anisotropy of the local exchange field and/or to the field-induced anisotropy of the magnetic susceptibility. In DMS the latter is shown to affect the position and the shape of the maximum in the magnetic-field dependence of CMR.

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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