Volobuev V. Thermoelectric and magnetic properties of semiconductor superlattices EuS-PbS.

Object of investigation - low dimensional semiconductor structures and size effects in them. Aim of investigation - establishment of conformity of size effect influencing on the magnetic and thermo-electric properties superlattices EuS-PbS. Methods of investigation: X-ray diffraction, electronic microscopy, photoluminescence, measuring of electric conductivity and termo-emf, neutron diffraction, SQUID, the magneto-optical Kerr effect. Theoretical and practical results: The interlayer exchange coupling between ferromagnetic layers via non-magnetic has been established for the first time in all-semiconductor superlattices, which results in antiferromagnetic ordering of magnetic layers (the magnetizations of the neighboring layers align in opposite direction). First, the substantial increase of thermoelectric power is experimentally shown for superlattices EuS-PbS with the small thickness of layers PbS ~ 1nm in comparison to bulk crystals and films of PbS. For the first time, the layer interdiffusion coefficients of layer materials were determined, activation energy end preexponential factor were estimated. It was established that the size of intermixing zone which was forming during the preparation of the superlattices did not exceed one monolayer. First, for degenerate electron gas in superlattice with Кronig-Penny potential taking into account dependence of electron effective mass from energy at impurity electron scattering superlattice thermo-electric characteristics (Seebek coefficient, conductivity, power factor and electronic heat conductivity) were calculated. The results of computations well conform to experimental data for superlattices EuS-PbS. Field of application: physics of semiconductors, physics of low dimensional structures, spintronics.