The electronic structure and magnetic properties of Heusler alloys (Ni 2 FeIn) have been studied by first principle calculations. The possible tetragonal martensitic transformation has been predicted and the structure optimization was made on cubic austenitic Ni 2 FeIn in Cu 2 MnAl type. The equilibrium lattice constant of austenitic Ni 2 FeIn is 6.03Å. In tetragonal phase, the global energy minimum occurs at c/a = 1.29. The corresponding equilibrium lattice constants for martensite Ni 2 FeIn are a = b = 5.5393Å and c = 7.1457Å, respectively. In the austenitic phase, E F is located at the peak in the minority DOS for c/a = 0.96 to 1.20, but in the martensitic phase, E F moves to the bottom of the valley in the minority DOS, reducing the value of N(E F ) effectively. Both austenitic and martensitic phases are ferromagnetic and the Ni and Fe partial moments contribute mainly to the total moments. Therefore, the martensitic transformation behavior in Ni 2 FeIn is predicted.
Self-assembled InAs quantum wires (QWRs) are fabricated on an InP substrate by solid-source molecular beam epitaxy (SSMBE). Photoluminescence (PL) spectra are investigated in these nanostructures as a function of temperature. An anomalous enhancement of PL intensity and a temperature insensitive PL emission are observed from InAs nanostructures grown on InP substrates using InAlGaAs as the matrix layer and the origin of this phenomenon is discussed. We attribute the anomalous temperature dependence of photoluminescence to the formation of Al-rich and In-rich region in the InAlGaAs buffer layer and the cap layer.
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