Ab initio study of Heusler alloys Co₂XY (X = Cr, Mn, Fe; Y = Al, Ga) under high pressure

Abstract

The structural, electronic, and magnetic properties of ferromagnetic Heusler alloys Co₂XY (X = Cr, Mn, Fe; Y = Al, Ga) have been investigated by means of the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation for the exchange and correlation potential. The main focus of this study is to elaborate the changes brought about in the electronic and the magnetic properties by applied pressure. The calculated total spin magnetic moments of all the compounds are found to be in good agreement with experiments. Out of these compounds, Co₂CrAl is found to be perfectly half-metallic (HM) and the other compounds are found to be nearly HM. Thus the HM to metal transition was observed at 75 GPa pressure for Co₂CrAl and the nearly half-metal to half-metal transition was observed at 40 GPa and 18 GPa for Co₂CrGa and Co₂MnAl, respectively, while no transition is observed in other compounds under investigation. It can be clearly seen that pressure affects the minority spin states rather than the majority states, leading to a slight reconstruction of the minority spin states with a shift in the Fermi level driving the above-mentioned transition.

Keywords:

• alloys
• ab initio calculations
• high pressure
• electronic structure
• magnetic properties