Effect of electron correlations on structural phase stability, magnetism, and spin-dependent transport in CeMnNi₄

First-principles calculations are carried out to study the effect of electron correlations on relative structural stability, magnetism, and spin-dependent transport in CeMnNi₄ intermetallic compound. The correct description of Coulomb repulsion of Mn3d electrons is shown to play a crucial role in reproducing the experimentally observed cubic phase of CeMnNi₄ as well as its relatively high degree of transport spin polarization (∼66%). These are the two fundamental properties of this compound which conventional density-functional theory approaches fail to predict correctly. The reason for this failure is attributed to an extreme overdelocalization of Mn3d charges causing a strong d-d hybridization between Mn and Ni atoms in the orthorhombic phase. Such an artificial hybridization, in turn, lowers the relative total energy of the orthorhombic phase with respect to the cubic one. It also leads to an incorrect carrier concentration and mobility at the Fermi level and, consequently, yields much lower degree of transport spin polarization for this nearly half-metallic compound.