1. P.I.Nikitin and A.I.Savchuk, Sov.Phys.Usp., 33, 974 (1990). 2. P.I.Nikitin et al., JETP Lett., 52, 274 (1990). 3. Y.Shapira et al., Phys.Rev.B, 30, 4021 (1984) 1. 4.
THE FARADAY EFFECT IN DILUTE MAGNETIC SEMICONDUCTORS IN ULTRAHIGH MAGNETIC FIELD O.M.Tatzenko, I.M.Markevsev, A.I.Pavlovskii, V.V.Platonov, P.V.Sosnin (Russian Experimental Physics R&D Institute), V.V.Druzhinin (Moscow Engineering & Physical Institute), A.S.Lugutin (Kurchatov Atomic Energy Institute), P.I.Nikitin, General Physics Institute, 38, Vavilov str., Moscow, Russia 117942 A.I.Savchuk, Chernovtzi State University Magnetic field dependencies of Faraday rotation (FR) and a magnetoabsorption in dilute magnetic semiconductors Cdl-xMnxTe in ultrahigh magnetic fields up to 500 T at room temperature have been experimentally investigated. Diluted magnetic semiconductors are alloys in which atoms of a semiconductor of 11-VI type are randomly replaced by magnetic atoms. Such alloys exhibit many interesting properties [l]. One of their unique features is the gigantic FR effect. It is due to large spin splitting in the band states of electrons, holes and excitons, as well as by the exchange interaction between band carriers and localized magnetic moments of Mn2+ ions. A stepped magnetic field dependence of the FR of the dilute semiconductors was observed in fields up to 25 T at a temperature T = 4.2 K [2]. This fact provides a direct determination of the antiferromagnetic exchange constant between the nearest-neighbour Mn2+ ions. The reported anomalies were shown to be related to a stepped change in the magnetization of the magnetic subsystem [3]. To observe such phenomena at T= 300 K fields much greater 30 T are required In present paper ultrahigh magnetic fields have been produced by MC-1 generator [4]. Cdl-xMnxTe samples used in the experiments are monocrystals with concentrations x = 0.43 and 0.45 and thicknesses of 0.1-0.3 mm. The experiments have been performed at two wavelengths A1 = 0.63 U and A2 = 1,06 N. For B 2 6 0 T experiments show stepped FR dependencies on magnetic field. In the whole range of magnetic fields, the absorption proved to be constant. At A1 wavelength we manage to resolve I= Iocos2 8 signal
only in fields up to 70 T due to large Verdet constant, which is equal to 1 . 5 ~ 1 0deg1T.m ~ or 6.8-103 deg1T.m at A2 wavelength. At wavelength A1 for fields up to 70 T there is no tendency to saturation. To describe FR dependence on B in this spectral range besides exchange and exciton contributions one should take into account the interband contribution [l]. As well as steps the FR dependence upon magnetic field at fields above 100 T and the wavelength A2 has a saturation that corresponds to the total Mn2+ ions spin alignment at S&B 2 kT. The experimental curve is adequately described by Brillouin function [5] n2
with the constant F = 400 (here B is Brillouin function). The deviation appearing at H > 150 T reflects the direct Zeeman splitting of exciton spin states [3]. In small magnetic fields this contribution is negligible due to the considerably large value of N(Jh-Je) [2], where J are the exchange interaction integrals. * The features of the magnetic field dependence of Faraday effect observed, which are associated with stepped variation of the magnetization of the subsystem of Mn2+, ions point to the opportunity of using this effect to study the exchange interactions of magnetic ions with band carriers in dilute magnetic semiconductors. References 1. P.I.Nikitin and A.I.Savchuk, Sov.Phys.Usp., 33, 974 (1990). 2. P.I.Nikitin et al., JETP Lett., 52, 274 (1990). 3. Y.Shapira et al., Phys.Rev.B, 30, 4021 (1984)1 4. A.I.Pavlovskii et al., Megagauss Technology and Pulsed Power Applications/eds. C.M.Fowler et al., Plenum Press, NY (1987). 5. D.U.Barthlomew et al., Phys.Rev.B, 34, 6943 (1986).
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