Luminescence of Cd0.7Mn0.3Te Crystals in Transverse Magnetic Field

Abstract

Photoluminescence of cleaved Cd 0.7 Mn 0.3 Te crystals is studied at T ≈ 1.6 K at the normal-and oblique (45 • ) incidence of the pumping Ar laser beam (λ = 488 nm) in magnetic fields −7 ≤ B ≤ 7 T in the Voigt geometry. At B = 0, photoluminescence maximum is found at 2.0819 eV at normal incidence (and backward emission) whereas the oblique incidence and emission shows photoluminescence maximum intensity at 2.0536 eV. The red shift of photoluminescence maximum position with the rise in B is observed and the results are found to be in good agreement with sp−d exchange interaction model for the oblique incidence case. Backward emitted photoluminescence line is found to narrow from 26.2 to 23.5 meV with the rise in B from 0 to 7 T. Alloy disorder contribution exhibits opposite trend to broaden, as is calculated on the basis of the matrix of the energy gap dependence on x and B. Therefore the observed photoluminescence line narrowing is assigned to the suppression of magnetic fluctuation in magnetic field. A linear size of magnetic fluctuation is estimated to be about 1/5 of the free exciton diameter. Photoluminescence maximum position difference in the normal-and oblique incidence cases is assigned to polaritons.

Luminescence of Cd0.7Mn0.3Te crystals in magnetic field: Linewidth, Landau quantization, and carrier effective mass

“…We continue our investigation of Cd 0.7 Mn 0. 3 Te luminescence in magnetic field and present broader analysis of effective band gap narrowing not only in terms of s, p − d exchange interaction theory approximation, which was performed in our earlier work [5]. This paper also extends our previous investigation of the influence of magnetic field on the luminescence linewidth (FWHM) value.…”

“…In the bcwd measuring geometry the magnetic field so steeply quenches the number of luminescent transitions that although the main spectral maximum moves towards lower energies in magnetic field, the other spectra with applied magnetic field remain in the area covered by the B = 0 T spectrum. Two additional narrow peaks of considerably less intensity with spectral position not depending on magnetic field were also observed in luminescence spectra of Cd 0.7 Mn 0.3 Te (more details are reported in [5]). …”

“…Till now we have analysed the value of energy of π transition but experimental results show that the changes of energies of σ and π transitions in magnetic field nearly coincide, with slight differences exceeding the error bar limits. Equality of energies of σ and π transitions in that approximate model is proved by us in [5] assuming the σ component of emission as the superposition of two components σ + and σ − .…”

“…Magnetic field was perpendicular to the direction of incident beam (Voigt geometry). Experimental set-up details are reported in [5].…”

“…Analysis of the line's full width at half maximum in this work is concentrated on the composition-disorderinduced broadening and on the magnetic part in broadening due to magnetic impurities. In our previuos work [5] the evaluation of composition-disorderinduced broadening was obtained using the formalism of binomial distribution to describe the random cation distribution in the excitonic volume V exc [10,11]. The standard deviation of compound composition within the excitonic volume given by binomial distribution is σ x = x(1 − x)/(K V exc ), where K is the density of cations in the crystal.…”