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A ballistic, coherent transmission system that utilizes the magnetic and electric barriers as Boolen input variables to realize functions similar to the conventional logic gates, is proposed. A device is used to propose construct based on the high-electron-mobility transistor (HEMT) with ferromagnetic (FM) and nonmagnetic (NM) metal gates deposited on top of the HEMT heterostructure.

Empirical pseudopotential (EPM) and virtual crystal approximation methods facilitate the evaluation of the band structure of Zn(1 - x)CdxSySe(1 - y) quaternary alloy. EPM is characterized by a pseudopotential substituting the atomic potential. Accuracy of evaluation of energy bands is ensured by manipulating a set of atomic factors. Band gap energy and composition of the alloy are correlated in a nonlinear manner. Effective mass, a device parameter of semiconductors, and its reciprocal are experimentally demonstrated to be monlinear functions of composition. The pseudopotential for cubic semiconductors of the zinc-blende kind can be expressed as the sum of antisymmetric and symmetric for factors.

Several studies are conducted to examine the long range exchange coupling taking place in the zinc-blende CrTe/ZnTe/MnTe trilayer. The shifts exhibited by the magnetic hysteresis loops of the compounds are also analyzed.

The low temperature molecular beam epitaxy technique is employed to explain the antiferromgnetic thickness dependence of the CrTe- MnTe exchange-bias system. The coercivity and the exchange bias field of the system are shown to be completely dependent on the thickness.

Magnetic imaging study of regular hexagonal shaped NiFe elements arranged in different configurations is described. The alternating chirality of the hexagons has disappeared when the interelemental spacing becomes large and the results are understood by the symmetry and direction of the stray field generated by the individual elements.

The optical, magnetic and transport behaviors of [Ge.sub.1-x][Mn.sub.x]Te grown by solid-source molecular-beam epitaxy are examined. The magnetoresistance of [Ge.sub.1-x][Mn.sub.x]Te is isotropic and has displayed a clear hysterestic loop at low temperature, which has resembled that of giant-magnetoresistance granular system in solids.

The magnetic properties of Si doped with transition-metal (TM) using ion implantation are studied. A range of analytical transmission electron microscopy (TEM) methods are used for examining the origin of the ferromagnetic in this system.

A systematic study of the structural and magnetic properties of molecular-beam epitaxial growth of CrTe thin films with different layer thicknesses and Cr/Te flux ratios is reported. The results obtained from high-resolution transmission electron microscopy reveal that a metastable zinc-blende (ZB) phase of CrTe film can be generated with a nominal thickness of 5 nm under suitable growth conditions.

The structural, transport and magnetic behaviors of (Zn,Cr)Te system without additional carrier doping grown by low temperature molecular-beam epitaxy on GaAs (100) substrates are investigated. The results have highlighted the importance of clustering effect in models for the diluted magnetic semiconductor (DMS) system and also the affect of disorder on the Curie temperature.

The growth and magnetic properties of BeTe with Cr doping grown on GaAs(001) substrate at Te-rich condition by solid-source molecular-beam epitaxy is presented. Results show that the ferromagnetic ordering of Be(Cr)Te films could be attributed to precipitations of NiAs C[r.sub.1-[delta]]Te.

A ballistic device model which harnesses the Dresselhaus spin-orbit coupling effect to induce spin polarization [P] is proposed. Calculations for GaAs, GaSb, and InSb show a field enhancement of [P] from peak 2%-3% to 10%-80% near the conduction band.

A device model is produced that couples spin to the crystal field, external magnetic, and transverse electric field E(sub y), such that current j(sub x) transport in the ballistic regime. As E(sub y) modulates j(sub x) and its polarization P at a particular distance y, the model shows that the Landau spin-orbit system could implement the functions of a spin-field effect transistor.

A drift-diffusion transport model to evaluate the spin-injection efficiency eta and magnetoresistance (MR) ratio in a ferromagnetic (FM) metal-semiconductor (SC)-FM metal trilayer structure is presented. The presence of interfacial resistances (IR) at the FM-SC boundary is found to be crucial for generating a large spin splitting of mu, and consequently a high injection efficiency eta.

The hydrostatic pressure dependence of Ge nanocrystals embedded into SiO2 matrix on the quartz-glass substrate by Raman scattering at room temperature is studied. A simple elastic model, which describes the effective pressure transmitted from matrix to the nanocrystals, is used to explain the results.