Influence of ferromagnetically ordered ion spins on a conduction electron

“…If the depth of the potential well introduced by the transition metal is much smaller than the width of the relevant band, second-order perturbation theory can be applied in order to evaluate corrections to the molecular-field and virtual-crystal approximation [40]. By contrast, for large and attractive exchange and alloy potentials, such that the potential well associated with the transition metal is deep enough to almost form a bound state, the corrections have to be described by a non-perturbative approach [41].…”

Section: Beyond Molecular -Field and Virtual -Crystal Approximationsmentioning

confidence: 99%

From Magnetic Polarons to Ferromagnetism

Dietl

1998

Acta Phys. Pol. A

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A brief overview is given on selected effects of the exchange coupling between effective mass electrons and localized spins in II-VI semiconductors containing Mn ions. In the case of a carrier or exciton trapped by an impurity or defect, the exchange interaction leads to zero-field spin-splitting.The current theory of such complexes, known as bound magnetic polarons, describes correctly their spectroscopic and thermodynamic properties as well as their formation dynamics. At the same time, a free magnetic polarona delocalized carrier accompanied by a traveling clond of polarized spinsis not expected to exist for the actual values of the coupling constants. However, hołe scattering by thermodynamic and static fluctuations is shown to affect significantly its energy. For a strong coupling, the corresponding renormalization has to be described by a non-perturbative approach. Finally, the influence of the carrier liquid upon the Mn spins is discussed. Here, either optical pumping or p-type doping may lead to a ferromagnetic order, both in bulk and layered structures. Because of a long-range character of the carrier mediated interactions, this ordering is not destroyed by the fluctuations, even in the reduced dimensionality systems.

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“…These effects were observed in bulk CdMnTe [2][3][4], ZnMnTe [5], ZnMnSe [6,7] and CdMnS [8]. The exchange contribution to the energy gap reflects a correlation between spins of the magnetic ions [9,3,7] and, therefore, it is particularly important in concentrated alloys possessing magnetically ordered (spin-glass or antiferromagnetic) phases [1]. However, bulk materials of single crystallographic phase are available only in a limited concentration range (x < 0.75 in the case of CdMnTe [1], and x < 0.80 for ZnMnTe [1]).…”

mentioning

confidence: 97%

“…Variation with temperature of the energy gap in DMS (as well as in magnetic semiconduction [14]) results from two effects: a nonmagnetic effect, reflecting phonon-induced lattice constant variation with T, typical of nonmagnetic semiconduction [15] and the mentioned above exchange correction to the conduction and valence bands [9,2,3,16]. The exchange interaction between the bottom of the conduction band and the upper conduction band states as well as interaction between the top of the valence band and the lower valence band states yields a red shift of the energy gap [9,2,3,7].…”

mentioning

confidence: 99%

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Temperature Dependence of Energy Gap of Highly Concentrated Cd_1-xMn_xTe(0.6 < x ≤ 1.0) Epilayers

et al. 1995

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The temperature dependence of the energy gap of MBE grown Cd1-x Mnx Τe (0.6 < x < 1.0) was measured for 2 K < Τ < 200 K and B < 5 Τ. The results are interpreted in the frames of the model predicting that the exchange contribution to the band edge shift is proportional to the product of the magnetic susceptibility and the temperature. 4,10]. In this communication we report on the energy gap variation with the temperature in Cd1-xMnxTe epilayers with Mn concentration ranging from x = 0.6 to x = 1.0 (i.e. in cubic MnTe).The samples used for the present study were grown by MBE technique as a few microns (< 5 μm) thick epilayers of cubic Cd 1 -x Mn x Te, on GaAs substrate.The manganese concentration was x = 0.66, 0.73, 0.85 and 1.0 (MnTe), as determined from the epilayer lattice constant. We measured the reflectance in the free exciton range for 2 K -< Τ < 200 K and magnetic flelds B < 5 Τ. In most cases the excitonic stuctures were not viSible in a standard reflectance experiment, irrespective of the applied magnetic field, most probably due to large exciton line width (913)

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Influence of ferromagnetically ordered ion spins on a conduction electron

Cited by 77 publications

References 7 publications

Magnetic order effects on electric susceptibility hole mass of Sn1-x MnxTe

Magnetic order effects on electric susceptibility hole mass of Sn1-x MnxTe

From Magnetic Polarons to Ferromagnetism

Temperature Dependence of Energy Gap of Highly Concentrated Cd_1-xMn_xTe(0.6 < x ≤ 1.0) Epilayers

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Influence of ferromagnetically ordered ion spins on a conduction electron

Cited by 77 publications

References 7 publications

Magnetic order effects on electric susceptibility hole mass of Sn1-x MnxTe

Magnetic order effects on electric susceptibility hole mass of Sn1-x MnxTe

From Magnetic Polarons to Ferromagnetism

Temperature Dependence of Energy Gap of Highly Concentrated Cd1-xMnxTe(0.6 < x ≤ 1.0) Epilayers

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Product

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Temperature Dependence of Energy Gap of Highly Concentrated Cd_1-xMn_xTe(0.6 < x ≤ 1.0) Epilayers