Electrical and Computer Engineering Location: Thornton Hall C311
Add to Calendar 2019-03-27T13:00:00 2019-03-27T13:00:00 America/New_York Doctoral Dissertation Defense for Jianhua Ma Computational Investigation of Heusler compounds for Spintronics Application Abstract: Heusler compounds have become a large family of binary, ternery, and quaternary compounds that show a variety of diverse properties and attracted tremendous scientific interest in the spintronics. The extensive tunability of the Heusler compounds through chemical substitutions makes large potential for the family. Thornton Hall C311

Computational Investigation of Heusler compounds for Spintronics Application

Abstract: Heusler compounds have become a large family of binary, ternery, and quaternary compounds that show a variety of diverse properties and attracted tremendous scientific interest in the spintronics. The extensive tunability of the Heusler compounds through chemical substitutions makes large potential for the family.

In this dissertation, we first present first-principles density functional calculations of the electronic structure, magnetism, and structural stability of 378 XYZ half-Heusler compounds and 405 X2YZ inverse-Heusler compounds. We find that a “Slater-Pauling gap” in the density of states, in at least one spin channel is a common feature in half-Heusler compounds. We calculate the formation energy of each compound and systematically investigate its stability against all other phases in the Open Quantum Materials Database (OQMD). We represent the thermodynamic phase stability of each compound as its distance from the convex hull of stable phases in the respective chemical space and show that the hull distance of a compound is a good measure of the likelihood of its experimental synthesis. In addition, our calculations predict a number of hitherto unreported semiconducting (e.g., CoVSn, RhVGe), half-metallic (e.g., RhVSb), and near half-metallic (e.g., CoFeSb, CoVP) half-Heusler compounds to lie close to the respective convex hull of stable phases. In the inverse-Heuslers, our calculations predict 4 half-metals and 6 near-half-metals to lie close to the respective convex hull of stable phases. Thus these candidates may be experimentally realized under suitable synthesis conditions, resulting in potential candidates for various semiconducting and spintronics applications.  In the following the discovery, a series of half-metallic half-Heusler alloys are combined with MgO to create Heusler-MgO junctions. The capacity to keep half-metallicity and perpendicular magnetic anisotropy (PMA) in NiMnSb/MgO and CoTiSn/MgO junction with MnMn interface layer makes it to be potential candidates as electrode layers in Spin Transfer Torque Random Access Memory (STT-RAM) devices.  Finally, Using first-principles calculations of structural and magnetic properties, we identify several promising ferrimagnetic inverse Heusler half-metal/near half-metals can be the ideal candidate for hosting ultra-small, fast, and room temperature stable skyrmions.