Structural, electronic and magnetic properties of quaternary Heusler compounds CoYFeZ and CoYMnZ (Z = Si, Ge, Ga and Al):

Abstract

We have studied electronic and magnetic structural properties of quaternary Heusler alloys CoYXZ where X is a transition
metal with 3d electrons (X=Fe and Mn) and Z is the main group element (Z = Si, Ge, Ga and Al). These calculations were
performed by an ab-initio study based on the density functional theory (DFT) approach. We searched the most stable
structure of our materials studied among three possible arrangements (type-1, type-2, type-3). The structural stability of
quaternary Heusler CoYXZ alloys (X = Fe and Mn, Z = Al, Si, Ga and Ge) was studied by the calculation of their cohesion
and phonon energies. The type-1 structure is found energetically the most stable. According to our study, the quaternary
Heusler CoYMnGa and CoYMnAl alloys proves to be a half-metal ferromagnetic with a total magnetic moment of 4.00μ
B.
While the quaternary Heusler CoYMnGe and CoYFeZ (Z=Al, Si, Ge and Ga) alloys, seem to be not ferromagnetic, with
zero moment magnetic. The quaternary Heusler CoYMnSi and CoYMnGe alloys are found ferromagnetic with magnetic
moment of 1.91 μ
B and 2.90 μ
B respectively. In addition, it is also divulged that half-metallicity in these compounds is closely
related to arrangements of magnetic atoms in Heusler alloys. The magnetization of the compounds CoYFeZ and CoYMnZ
comes mainly from the 4d electrons the of Yttrium (Y) atom and the 3d electrons of the Fe and Mn atoms.