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The electronic structures of tetragonally distorted half-Heuselr compound LaPtBi in the C1 b structure are investigated in the framework of density functional theory using the full potential linearized augmented plane with local spin density approximation method. The calculation results show that both the band structures and the Fermi level can be tuned by using either compressive or tensile in-plane strain. A large bulk band gap of 0.3 eV can be induced through the application of a compressive in-pane strain in LaPtBi with the assumption of a relaxed volume of the unit cell. Our results could serve as a guidance to realize topological insulators in half-Heusler compounds by strain engineering. ___________ a) Electronic

By using one ultrathin NiO layer to replace the Pt capping layer in the Co/Pt multilayer with perpendicular anisotropy, we present direct evidence for the existence of antiferromagnetic interlayer coupling between the Co layers through the Pt layers thicker than 24 Å. The NiO capping layers play two key roles in the observation of antiferromagnetic interlayer coupling. One is the manipulation of the coercivity of the Co layer in contact with the NiO layer, the other is the enhancement of the electron reflectivities at the Co/Pt interfaces via the specular scattering effect at the Co-NiO interface. The thermal variation in the magnetization of the Co layer also plays an important role in the observed antiferromagnetic coupling due to its strong effect on the phase of electron reflectivity at the Co/Pt interfaces. The magnetization-dependent phase can lead to the ferromagnetic-antiferromagnetic transition of the interlayer coupling at high temperature. All these factors are combined together to realize the direct observation of antiferromagnetic interlayer coupling in the Co/Pt multilayer with perpendicular anisotropy.

By using first-principles calculations, we have systematically investigated the phase stability, magnetism and electron-filling behavior of vanadium-based inverse Heusler compounds. Our calculation results indicate that, due to the complex hybridization of the d orbitals for the vanadium atom, the electronic structures of the vanadium-based inverse Heusler compounds show two opened gaps (one locates in the spin-up channel and the other in the spin-down channel) near the Fermi level, originating from different bonding states. Based on the unique electronic structures, we proposed a generalized electron-filling rule, which can qualitatively explain the unusual change of the molecular spin magnetic moment as a function of the total number of valence electrons observed in the vanadium-based inverse Heusler compounds. Moreover, most of the vanadium-based inverse Heusler compounds have a negative formation energy, which indicates that they are promising to be synthesized experimentally.