Site Preference,Magnetic And Electronic Properties Of Half-metallic Vanadium-based Full Heusler Alloys

Heusler alloy is an excellent intermetallic material with an infinite number of members and a wide variety of properties ranging from topological insulators of superconductors of semi-metallic ferromagnets to ferromagnetic memory alloys.Heusler alloy of half-metal is widely used in condensed matter physics because of its characteristic of 100%spin polarization.And according to Slater-Pauling rule,its magnetism can be predicted and even regulated,which will be widely used in spintronic devices.In this paper,we focus on the design and development of new semi-metal for multi-functional applications.First principles are used to calculate the energy,magnetic moment,energy band structure and density of state of the alloy.Some alloys were obtained by non consumable arc melting and their crystal structures were determined by X-ray diffraction.The main content of this paper is divided into the following two parts:Part one,we reported a new atomic site preference occupation for Vanadium-based X2YZ full Heusler alloys.The traditional Heusler alloy placeholder is mainly dependent on the positive electrical properties of X bit atoms and Y bit atoms.When Y is the positive electrical property of the atom is greater than the positive electrical property of the X bit atom,the alloy should form L21 structure.Conversely,an XA structure should be formed.It tells that alloys with less 24 valence electrons form the L21-type structure,while others form the XA-type structure.This fact means that the site preference rule for Vanadium-based alloys depends on the total number of valence electrons instead of the electropositive between X and Y atoms.The magnetic moments of XA-type alloys follow the Slater-Pauling rules,with two forms,Mt=NV-24 and Mt=NV-18 corresponding to different origins of the band gaps.XA-type V2YZ(Y=Cr,Mn and Fe;Z=Ga,Ge and As),V2CoGa,V2CoGe and V2NiGa alloys have half-metallic property.L21-type V2YZ(Y=Cu and Zn;Z=Ga,Ge and As)alloys show no spin polarization and no half-metallic property due to the structural symmetry and the non-magnetism of copper and zinc atoms.And the PDOS of some L21 alloys were calculated and the magnetic moment provided by each atom was explored.Part two,We are committed to looking for fully compensated ferrimagnet spin gapless semiconductors(FCF-SGSs)which integrates the advantages of half-metal 100%spin polarization,half-metal anti-ferromagnetic,spin gapless semiconductors,etc.According to the slater-pauling rule,the Heusler alloy with 18,24,28 valence electrons can obtain zero net magnetic moment.So we take Heusler alloy with this valence electron number as the research object.Based on the first principle,these Heusler alloys were calculated and the alloys containing AFM-SGS,HF-AFM and AFM-SM.We found that the composition and structure type of Heusler alloy are important factors affecting the formation of antiferromagnetism.By further analyzing the state density of the alloy,it is found that the alloy with valence electron number of 18 can easily obtain AFM-SGS and AFM-SM;alloys with a valence electron number of 24 can easily obtain HF-AFM;AFM-SGS and AFM-SM can be obtained only in a few alloys with a valence electron of 28.These results reveal that Heusler alloys are an outstanding class of materials with a large variety of diverse properties.The search for new,multi-functional Heusler alloys are still a fruitful field of research in coming years.