Influence of L2B Disorder on the Spin-Gapless Semiconductor Character in Quaternary Heusler Alloys CoFeMnSi and CoFeVSi.

The relative stability between disordered L2B structure and ordered XA structure in Heusler alloys CoFeVSi and CoFeMnSi has been compared by using first-principles calculations. It has been found that the L2B structure is lower in energy and stable in CoFeMnSi while in CoFeVSi, the ordered XA structure has a higher stability. The SGS character in XA-type CoFeVSi and CoFeMnSi may be disturbed by L2B disorder. CoFeMnSi becomes a half-metal while CoFeVSi becomes a normal ferromagnetic metal when L2B disorder occurs. The SGS character in XA-type and half-metallicity in L2B-type CoFeMnSi are insensitive to lattice distortion, which is interesting to technical applications. Finally, our results suggest that the relative stability of L2B structure and XA structures in Heusler alloys may be composition dependent, and the possibility of L2B structure should be considered, when designing and preparing Heusler alloys. [ABSTRACT FROM AUTHOR]