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Photoluminescence in EuS-PbS-EuS semiconductor structures with double ferromagnetic barrier

Kowalczyk L., Chernyshova M., Story T., Sipatov A.Yu.

Materials Science Poland

2006

Vol. 24, No. 3

809--814

Temperature, magnetic field and laser excitation power dependence of the photoluminescence (PL) was studied in 5x[EuS(5.5 nm)-PbS(17.5 nm)] semiconductor ferromagnetic multilayer grown epitaxially by high vacuum deposition on BaF2 (111) substrate. In EuS-PbS heterostructures ferromagnetic layers of EuS form electron barriers for both electrons and holes in nonmagnetic quantum wells of PbS. The PL was observed in the near infrared due to electronic transitions in PbS quantum wells with narrow energy gap. The measurements carried out at T=4.2 and 77 K (i.e. below and above the Curie temperature of EuS layers equal about 14 K) showed the characteristic PL spectra consisting of one or two lines with strongly nonlinear response upon increasing the YAG laser excitation power. Below the Curie temperature, the application of a weak magnetic field of 200 Oe results in a change of the PL intensity as well as a small red shift of about 1 meV of the PL energy. These observations are discussed in terms of a model taking into account the magnetization dependent height of EuS potential barrier for electrons in PbS quantum well.

Influence of in dilution level on magnetic mroperties and photoconductivity of Cd1-yCr2-2xIn2x+ySe4 magnetic semiconductors

Cięciwa B. T., Maksymowicz L. J., Lubecka M., Jankowski H., Sokulski J., Sobków Z.

Materials Science

2003

Vol. 21, No. 1

98-106

Magnetic semiconductors of CdCr2Se4 diluted by indium belong to the class of soft magnetic materials. The amount of indium alters the energetic structure of chalcogenide spinel. For CdCr2Se4 : In magnetic semiconductor the state with reentrant transition (REE) is achieved. In the case of Cd1-yCr2-2xIn2x+ySe4 dilution the spin glass (SG) state and the randomly canted state is obtained. Chalcogenide spinel could be used as the element of a near-infrared detector. Then the photoconductivity properties are in our interest and they are presented by the voltage sensitivity versus the light wavelength. This parameter is also affected by the dilution level. The polycrystalline thin films of Cd1-yCr2-2xIn2x+ySe4 obtained by rf sputtering technique are studied. It was found that the voltage sensitivity of the photoresponse vs. the wavelength differs significantly for samples with REE and in the SG state. For both types of magnetic ordering the photoresponse below the critical magnetic temperature is bigger then for temperature above this one.