Effect of Co substitution on Ni₂MnGe Heusler alloy: ab initio study

Ab initio calculations shown that the Co substitution instead of Ni in Ni₂MnGe with the L2₁ crystallographic structure leads to a decrease of the lattice constant and an increase of the total magnetic moment of the Ni_{2-x}Co_{x}MnGe compounds. The Mn(B) has the largest local moment above 3 μ_{B} coupled parallel to moments on the Ni(A,C) and Co(A,C), which are found in the ranges of 0.19÷0.26 μ_{B} for Ni(A,C) and 1.03÷0.97 μ_{B} for Co(A,C) for studied range of x. Using the results stemming from the total energy calculations, the values of bulk modulus and its pressure derivatives are estimated according to the Murnaghan EOS.