Robust half-metallic spin-gap in Co2CrAl: doping and strain engineering

Half-metallic ferromagnetic (HM FM) materials with sizeable HM-gap have grabbed a lot of attention as they provide high spin-filtering and reduce the spin-flipping, which are necessary parameters for the manufacturing of magnetic memory devices. Herein, the effect of 3d transition metals (TM = Ti, V, Mn, and Fe) doping at Cr site on the electronic and magnetic properties of full-Heusler Co2CrAl compound is investigated utilizing ab-initio calculations. The negative formation energies for all doped systems confirm their structural stability at ambient pressure. Our results revealed that undoped and all the TM-doped systems exhibit a stable HM FM state. The Cr d(yz) and d(3z2-r2) orbitals are mainly responsible for conductivity in the spin-majority channel with a small contribution from d(xy/)d(x2-y2) states in each case. It is also found the admixture of t(2g) and e(g) characteristics of TM ions in the spin-magnetization density iso-surfaces, where magnetism is discussed by analyzing the electronic spin state configurations. Moreover, it is found that half-metallicity in all systems is robust and can be preserved by the compression/elongation of the unit cell volume up to 10%. Finally, the Bader charge analysis exhibits that all the motifs contain a mixture of covalent and ionic characteristics. Hence, the present work suggests that 3d TM-doped Co2CrAl structures are of great interest for the development of extremely capable data storage devices.