Structural Disorder and Magnetism in the Spin-Gapless Semiconductor CoFeCrAl

• Main Authors: Choudhary,Renu, Kharel,Parashu, Valloppilly,Shah R, Jin,Yunlong, O'Connell,Andrew, Huh,Yung, Gilbert,Simeon, Kashyap,Arti, Sellmyer,D J, Skomski,Ralph
• Format: Report
• Language: English
• Subjects: alloys; annealing; band gaps; density functional theory; Ferrimagnetism; magnetic properties; Semiconductors; Superlattices

Disordered CoFeCrAl and CoFeCrSi0.5Al0.5 alloys have been investigated experimentally and by first-principle calculations. The melt-spun and annealed samples all exhibit Heusler-type superlattice peaks, but the peak intensities indicate a substantial degree of B2-type chemical disorder. Si substitution reduces the degree of this disorder. Our theoretical analysis also considers several types of antisite disorder (Fe-Co, Fe-Cr, Co-Cr) in Y-ordered CoFeCrAl and partial substitution of Si for Al. The substitution transforms the spin-gapless semiconductor CoFeCrAl into a half-metallic ferrimagnet and increases the half-metallic band gap by 0.12 eV. Compared CoFeCrAl, the moment of CoFeCrSi0.5Al0.5 is predicted to increase from 2.01 B to 2.50 B per formula unit, in good agreement with experiment. AIP Advances , 6, 5, 01 Jan 0001, 01 Jan 0001, Open Access: Publishers Version. May be placed on public websites; Creative Commons Attribution 3.0 Unported License.