Browsing by Author "MAAFA Amina"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Ab-initio Study of the Physical Properties of Heusler Alloys
    (2021-11-14) MAAFA Amina; Encadreur: ROZALE Habib
    Abstract : Since their discovery, half-metallic ferromagnets have been the topic of many theoretical and experimental researches due to their potential applications. The well-known Heusler compounds have attracted most attention as several among them were predicted to be half metals. The family of Heuslers incorporates thousands of members exhibiting diverse magnetic phenomena, which makes them very useful in various contemporary fields such as spintronics. For this reason, we have been interested in the ternary most explored group of Heusler alloys as well as their quaternary daughter systems. At first, we have investigated a set of Co- and Fe-based ternary systems (X = Fe, Co; Y = Zr, Mo and Z = Ge, Sb) using ab-initio calculations. We found that Cu2MnAl type structure is more favorable for all compounds, except X2MoGe (X = Co, Fe) and Co2MoSb where the inverse structure was energetically more stable. After studying the electronic properties, we have identified two half-metals (Co2ZrGe and Fe2ZrSb) that could be potential for spintronics applications. Unlike Fe2ZrSb, the half-metallicity in Co2ZrGe alloy has already been predicted in few theoretical studies where the structural and electronic properties agree well to our results. We have also checked the mechanical properties of the ternary alloys. The elastic parameters indicated the mechanical stability of the four Fe2ZrSb, Co2ZrGe and Fe2MoZ (Z = Ge, Sb) materials, where the half-metallic Fe2ZrSb compound is the only one characterized by an enhanced ductility. Afterwards, we completed the previous study by forming eight quaternary structures using the same previous magnetic components. We have studied the physical properties of the quaternary XX’YZ alloys (X = Co, Fe; X’ = Mo, Fe; Y = Zr, Fe; Z = Sb, Ge) and explained their relation with the former ternary Heuslers. The DFT method was once again applied to investigate the magnetic nature of these alloys and we found two other half-metals (CoFeZrGe and CoFeZrSb). Actually, both materials have already been investigated and the resulting lattice constants and gaps were close in values to our theoretical calculations. Additionally, we have computed the elastic parameters, electronic properties as well as the thermoelectric efficiency of the quaternary XX’YZ alloys. They were found to be mechanically stable and have shown different degrees of ductility and stiffness. Besides, they could be very v efficient for the thermoelectric field applications, which paves the way for further theoretical and experimental investigations concerning these new Heuslers.