The College of Education for Pure Sciences, Physics Department, reviewed a doctoral dissertation on surface and boundary analysis of Heussler half-alloys using density functional theory. The dissertation, submitted by researcher Hikmat Abdul Hussein Ibrahim, aimed to study the electronic and magnetic properties of Heussler half-alloys in the bulk state, at surfaces, and at the boundary. Heussler half-alloys exhibit semimetallic properties and spin polarization at the Fermi level. Therefore, they are important and necessary for the development of spin electronics devices.
The surfaces of the MnZrTe compound with Zr and Te terminals retained the semimetallic properties. Conversely, the semimetallic properties were lost at the manganese-terminated surfaces (Mn) and at the ZrTe-terminated surfaces (001). Furthermore, the semimetallic properties were destroyed at the boundary, while the boundary itself retained the semimetallic properties. Similarly, for the compound, surfaces with atoms were found to retain the semimetallic properties. The thesis also indicated that the configuration at the interface and secondary interface of a compound retains its semimetallic properties, whereas the Zr-Cd configuration, despite exhibiting significant polarization, does not retain its semimetallic properties. Regarding the properties of the MnZrGe semimetallic alloy, it was found that the surfaces terminated in (001)ZrGe, (001)Mn, (111)Ge, and (001)Zr retain their semimetallic properties. The semimetallic properties of MnZrGe were disrupted in both the (111)Ge-In and (111)Ge-As configurations at the (111)MnZrTe/InAs interface.
Calculations performed on MnZrTe, MnZrSi, and MnZrGe alloys at their respective crystal lattice constants revealed specific electronic properties: MnZrTe (6.20Å) has an energy gap (Eg) of 1.16 eV and a half-metal gap (EHM) of 0.26 eV; MnZrSi (5.97Å) exhibits an energy gap (Eg) of 1.19 eV and a half-metal gap (EHM) of 0.11 eV; and MnZrGe (6.09Å) exhibits an energy gap (Eg) of 1.06 eV and a half-metal gap (EHM) of 0.13 eV. In addition, the magnetic moments were found to be 1 μB for MnZrTe and 3 μB for both MnZrSi and MnZrGe
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