Magnetic and electronic properties of the RECu4Al8 (RE = Tb, Dy, Ho, and Er) intermetallic compounds

Spin density functional theory calculations were employed to study some of the magnetic and electronic properties of the RECu4Al8 (RE = Tb, Dy, Ho, and Er) intermetallic compounds in their tetragonal crystal structure and their collinear antiferromagnetic state. The exchange and correlation electronic effects were treated by both a generalized gradient approximation (GGA) in its recently revised version for solids (GGA-PBEsol), and the addition of the effective Hubbard U term (GGA-PBEsol + Ueff) in the RE 4f states. Based on these methodologies, the total magnetic moment of the RE atoms and their spin and orbital contributions were determined. The total magnetic moment calculated with GGA + PBEsol (Ueff = 0.0 eV) agreed with the experimental data, except for the TbCu4Al8 system, in which the addition of the Ueff term was needed for a better description. Using GGA + PBEsol, the magnetocrystalline anisotropy energy (MAE), easiest magnetization axis (EMA), exchange splitting of the RE 4f states (Δex), and the electronic specific heat coefficients (γ) of the four compounds were determined. The values of the MAE found for TbCu4Al8, DyCu4Al8, HoCu4Al8, and ErCu4Al8 were 3.13, 9.11, 26.93, and 17.41 meV/f.u., respectively. The EMA for TbCu4Al8, DyCu4Al8, and HoCu4Al8 was found to be [111], while for ErCu4Al8 it was [001]. The values of Δex were equal to 4.3, 3.6, 2.8, and 1.9 eV for TbCu4Al8, DyCu4Al8, HoCu4Al8, and ErCu4Al8, respectively.