Electronic structure and physical properties of half-metallic ferromagnetic compounds : a first-principles study

Abstract

Diluted magnetic semiconductors (DMSs) are a class of materials belonging to half-metallic materials which exhibit interesting characteristics such as lower energy consumption, and higher density, and speed data transfer. These materials have potential applications in spintronics and magnetic storage and optoelectronic devices. However, the physical properties of DMSs are highly dependent on their specific composition and structure, making them difficult to predict and control. In this thesis, first-principles calculations are used to study the structural, electronic and magnetic, and optical properties of CaTe and CaSe doped with V, Cr, and Mn elements with various concentrations. The focus is on understanding the relationship between the composition, impurity type and concentration effect of these materials and their properties based on density functional theory (DFT), which is a widely used method for studying the electronic properties of materials. As known that TB-MBJ functional gives results related to the occurrence of the band gaps, we used TB-MBJ to explore the electronic, magnetic, and optical properties of studied compounds. The chemical stability was confirmed with cohesion and formation energy. We found ferromagnetic configuration with 100% spin-polarization at Fermi level (EF) for Cr-doped CaTe and CaSe due to the presence of strong double exchange interaction, while V and Mn-doped CaTe and CaSe favor the antiferromagnetic configuration caused by the existence of antiferromagnetic superexchange interaction. These two exchange interactions are fueled by strong p-d exchange interaction. We found large half metallic gaps and high curie temperature (TC) for Cr-doped. The introduction of transition metal atoms creates energy levels that have a significant impact on the electronic and optical properties of a material, ultimately affecting the material's ability to absorb light. Armed with our expertise in these key properties, we candidate CaTe and CaSe-based DMSs for future spintronics applications in the years to come