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A aeo&ical invatigation is made of the Moasbauer shift in crystals containing exchange coupled magnetic ions. It is found that the shift is caused by the exchange interaction and &pen& on the degree of ordering of the spin system. PaccMOTpeH BOIIPOC 0 BeJlUYUHe CnBUra M0CC6ay3pOBCKOrO CIIeKTpa B KpUCTaJInax, conepWaUUX MarHUTHbIe HOHbI, CBFI3aHHbIe 06MeHHbIM B3aUMOnefiCTBHeM. BunCHeHO, 4TO 06MeHHbIe B3aUMOXeftCTBUfl npMBOn.RT K CnBHIY, 3aBMCcllrreMy OT CTeneHu ynopanosesun CnUH-CUCTeMbl.

The investigations of the optical properties of ferrospinels are usually carried out by means of magnetooptic methods i n the region of intraband d-d transitions /1/ o r in the lattice absorption region in the far IR.Based on room temperature measurements of the near normal reflectance the Kramers-Kronig analysis was used to find the spectral dependence of the absorption coefficient for some ferrites /2 to 4/. F o r the sample with a high c a r r i e r concentration (n * loz5 m-3) the behaviour of the optical constants in this spectral region w a s ascribed to the presence of the small polaron kind of charge carriers.Based on the investigations of the temperatures and frequency dependences of the electrical properties for a single crystal of Mn-Zn ferrite we made earlier a conclusion about the band nature of the charge c a r r i e r s in this magnetic semiconductor /5/. To obtain more information about the electron structure of Mn-Zn ferrites w e investigated the optical properties and photoconductivity of the single crystals Mno. 64Zno. 5Fel. 8604 and Mno. 55 Z?. Fel . 3504 in the spectral region 2500 t o 500 nm. Measurements were made in the temperature region 83 to 450 K. Non-polarized light was used. Ohmic contacts for the photoconductivity measurements were made by means of thermal evaporation of indium onto the chemically polished surfaces of the samples.In the spectra of both samples a fast growth of the absorption coefficient is observed at the photon energy h v = 0.75 eV (T = 293 K) (Fig. 1). This energy is in good agreement with the activation energy of the conductivity /5/.A "bluen shift of the absorption edge is observed when the temperature decreases. The sign of the shift in these samples is opposite to the sign of the shift in CdCr2Se4 and europium chalcogenides.1) Dostoevskogo 81 -43, Kazan-97, USSR.