Exploring half-metallic Co-based full Heusler alloys using a DFT+U method combined with linear response approach

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Half-metallic (HM) ferromagnets are crucial for spintronic devices.
• Ternary full Heusler alloys offer potential for HM properties.
• Accurate theoretical methods are needed to predict HM behavior.

Purpose of the Study:

• Investigate the electronic structures of Co-based ternary full Heusler alloys (Co2YSi).
• Explore the potential of these alloys as half-metallic ferromagnets with wide HM gaps.
• Develop and apply an advanced computational method for accurate predictions.

Main Methods:

• Employed a density functional theory (DFT)+U method.
• Utilized linear response (LR) theory for calculations.
• Extended the LR-based DFT+U method to ternary Co2YSi and quaternary Co2(Y,Mn)Si alloys.

Main Results:

• The LR-based DFT+U method showed limitations with Co site correlation but was reasonable for Y site.
• Identified that the HM gap in Co2MnSi arises from Co orbitals and Co-Mn hybridizing t2g orbitals.
• Co2(Ti0.25,Mn0.75)Si and Co2(Fe0.25,Mn0.75)Si exhibit HM nature with high thermal stability.

Conclusions:

• The HM gap in Co2YSi alloys is tunable by selecting the Y element or mixing elements.
• The LR-based DFT+U method, despite limitations, provides insights into HM properties.
• The studied quaternary alloys demonstrate promising characteristics for applications requiring thermally stable HM ferromagnets.