Resonant electron spin-flip Raman scattering in CdTe and the diluted magnetic semiconductorCd1−xVx

Stanislav Tsoi

¹

,

I. Miotkowski

²

,

S. Rodríguez

³

et al.

Abstract

Resonant enhancement enables the discovery and delineation of spin-flip Raman scattering ͑SFRS͒ from free or donor-bound electrons in diluted magnetic semiconductors containing 3d transition-metal ions at doping concentrations. In such studies, the intrinsic g factor of the host, CdTe in the present case, has to be accounted for accurately. The SFRS in CdTe yields the conduction band electron g factor of Ϫ1.676Ϯ0.007 and displays two resonance peaks mediated by free and donor-bound excitons, respectively. Excitonic signature in modulated reflectivity signals the successful formation of Cd 1Ϫx V x Te as an alloy, whereas magnetization measurements show vanadium ions incorporated as V 2ϩ with xϳ4ϫ10 Ϫ4 . SFRS of Cd 1Ϫx V x Te displays vanadium related SFRS shifts of a sign opposite to that of the host. This indicates a ferromagnetic s-d exchange interaction between the s-like conduction electrons and the 3d shell of V 2ϩ in Cd 1Ϫx V x Te; from the linear dependence of the s-d exchange energy as a function of magnetization ␣N 0 , the s-d exchange constant is deduced to be 285Ϯ8 meV.

Resonant electronic Raman scattering in a Van Vleck II-VI diluted magnetic semiconductor:Cd1−xFexTe

“…The Fe concentration was determined from the energy of the free excitonic signature ͓E gx ͑x͔͒ observed in wavelengthmodulated reflectivity at zero magnetic field, in conjunction with the calibration E gx ͑x͒ = 1.594+ 1.78x ͑eV͒ obtained by Testelin et al 20 Figure 5 shows electron SFRS spectra recorded for x = 0.024 at 2 K. The Raman shift of electron SFRS, equal to the Zeeman splitting of the conduction-band minimum, is given by 7,28 …”

“…the first term describing the intrinsic Zeeman splitting in the CdTe host, characterized by g * = −1.676, 7 and the second term, known as the s-d exchange energy, arising from s-d exchange interaction. In this expression, ␣N 0 is the s-d exchange constant, and ͗͗S z ͘͘ a thermal and spatial average of the magnetic ion spin projection on the direction of magnetic field.…”

“…In contrast, Co 2+ in Cd 1−x Co x Te possesses a ground state with an effective spin of 3 / 2, resulting from crystal-field and spin-orbit effects, which leads to a B 3/2 magnetization behavior. We recently showed 7 that vanadium enters CdTe as V 2+ , also exhibiting a B 3/2 behavior. The case of Fe 2+ is more complex.…”

Linear polarization of the photoluminescence of quantum wells subject to in-plane magnetic fields

“…The field-dependence of the ESF Raman shift is reasonably well described by a Brillouin function [ 9 ] plus the intrinsic conduction band Zeeman splitting with the following parameters: effective temperature T + T 0 = 3.8K (higher than the bath temperature of 1.5K because of antiferromagnetic coupling effects at the high Mn concentration of the barrier [ 12 ]); effective paramagnetic Mn concentration experienced by the quantum well electrons x = 0.0034; s-d exchange constant N 0 α = 0.22 eV, and conduction band g-factor for the quantum well of -1.3; this latter is altered from the intrinsic CdTe conduction band g-factor value of -1.67 [ 13 ] because of quantum confinement effects [ 11,14 ]. Several alternative sets of fitting parameters can be found but we have chosen the set most consistent with the previous work cited here.…”

Raman scattering in the diluted magnetic semiconductorZn1−xFexTe: A van Vleck paramagnet

“…3͒ shows an effective spin of ͑3/2͒ប and hence a B 3/2 Brillouin-type paramagnetism. Tsoi et al 4 showed that V 2+ in CdTe also displays a B 3/2 behavior. The magnetism of Fe 2+ in the DMS ternaries is distinctly different from those containing Mn 2+ and Co 2+ .…”