The most popular semimagnetic or diluted magnetic semiconductors (DMS) are materials with Mn, Co and Fe as the magnetic ions [1]. In all of them a strong exchange interaction between magnetic ions and band carriers has been observed. It seems rather well established . at in the materials the p-d exchange results mostly from the hybridization of d orbitals (3 t-type and 2 e-type) with the valence band. In the centre of the Brillouin zone only the t-orbitals hybridize with the valence band. From this point of view the situation for Mn-, Co and Fe-DMS is similar, since for all of them t-orbitals are singly occupied (Mn: d 5 = t3+e2+, Fe: d6 = t3+e2+e-1 , Co: d7 = t 3 + e 2 + e -2 ) . I n s u c h a c a s e , a s i m p l e i s o t r o p i c Heisenberg Hamiltonian constitutes a :odd approximation for the p-d exchange [2], and band splittings should be parametrized by macroscopic magnetization. In fact, such behaviour was encountered in the experiment [1]. The situation for Cr-DMS is different: two t orbitals are occupied and the remaining one is empty (d4 = t2+e2+). In this case non-Heisenberg term in the Hamiltonian are expected [2,3]. In view of that, we studied newly grown ZnCr e, with Cr concentration x < 0.005. Magnetoreflectivity from the (110) surface was measured in the range of the fundamental absorption edge at Τ = 2 Κ and an exciton line was observed. In the presence of a magnetic field (B = 0 -5 T, Faraday configuration) the exciton line splits into two components (each visible in one of the circular polarizations). We recall that for other DMS the exciton line splits into four components [1]: lines A, B (σ+ polarization) and C, D (σ-polarization). We believe that due to *Supported by the the Committee for Scientific Research (grant nr 2 0223 91 01). t On leave from Pedagogical University, Hanoi (902)

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)

ZnTe-Cd1-xMnxTe1-ySey heterojunctions were prepared by vaportransport epitaxy of ZnTe on In-doped Cd1-xMnxTe1-ySey (x = 0.05, y = 0.03) single crystalline substrate in vacuum. At temperatures lower than 120 K the infrared and red electroluminescence were observed from the ZnTe-Cd1-xMnxTe1-ySey diode with forward current density in the range 0.003-4.0 A/cm2 .

A recently proposed magnetooptical method of determination of interface mixing was applied to CdTe/CdMnTe superstructures grown by pulsed laser evaporation and epitaxy. Diffusion length were found ≈ 5 Ǻ for a multiple quantum well and > 15 Α for a superlattice. Ranges of Mn mole fractions and well width values enabling efficient application of the method were determined. PACS numbers: 73.20.Dx, 78.20.Ls, 75.50.Ppa It has been reported [1] that magnetoreflectivity can provide valuable information on interface quality in the CdTe/CdMnTe system. The Zeeman splitting of ground states of quantum wells with Cd 0 .7Mn0 . 3 Te barriers has been shown to be extremely sensitive to interface mixing between the nonmagnetic well and the barrier containing Mn++ ions, allowing to estimate the interface mixing range.In this work we test for the first time a superstucture grown using pulsed laser evaporation and epitaxy (PLEE) technique [2]. Besides testing the quality of the interface in the PLEE method, we shall try to estimate the useful range of the superstucture parameters, allowing efficient application of the magnetooptical method of interface characterization.In our experiment we analyzed two samples: a multiple quantum well (CCM108) with relatively large well thickness and a superlattice (CCM206). Samples were grown by PLEE method on (001) Cd0.95Zn0.05Te substrates. The multiple quantum well (MQW) contained 30 pairs of CdTe wells of nominal thickness 120 Α with 170 Α thick CdMnTe barriers. The superlattice (SL) contained 40 pairs of wells and barriers with thickness 20 Α and 95 Å , respectively. Both samples were grown on a CdMnTe buffer and covered by a CdTe capping layer.(571)