Phase diagram, structure, and magnetic properties of the Ge-Mn system: A first-principles study

Abstract

We study the whole Ge-Mn phase diagram with density functional theory (DFT) methods. The 16 known phases are described and trends are analyzed. The compounds are then simulated, allowing a complete evaluation of this method in the projector augmented-wave approach within the collinear spin-polarized framework. Structural parameters, as well as magnetic properties, are compared to experimental values. Stability issues are addressed using a thermodynamic approach based on the grand potential, showing good agreement with experimental data. The impact of semicore electrons and the exchange-correlation functional are also discussed. Finally, it is shown that DFT methods are well suited to study this system, provided that the generalized gradient approximation is used, as opposed to the local density approximation, and correlations between structural errors and Mn concentration are taken into account. In addition, the precision achieved when compared to experiments is 40 meV/atom on energy, ±3% on the lattice parameter, and 0.2μ B /Mn on magnetic moments. Magnetic orders are mostly well reproduced.

Thermodynamic study of the Ge–Mn–Si system

“…The same behavior is noticed for the magnetic moments of manganese on the 4a and 6g sites. The magnetic moments calculated for Mn 5 Si 3 are in good agreement with previous calculations of Arras [12] and in an acceptable agreement with the measurements of Forsyth [13].…”

Interface-driven phase separation in multifunctional materials: The case of the ferromagnetic semiconductor GeMn

“…21 However, the calculated formation energy reaches 180 meV/atom. 13 Applying the same approach as for the nT mS compounds, we have tested 45 different atomic configurations of Mn interstitials, using various cell sizes to have a complete energy diagram of all cubic Ge-based compounds. We have discovered a whole family of low-energy structures based on the Ge 2 Mn phase shown in Fig.…”

“…Let μ 0 A and μ 0 B be the chemical potentials when the phases γ and δ are at equilibrium (i.e., γ and δ represent the atom reservoirs) 13 :…”

Magnetic and electronic properties of D22-Mn3Ge (001) films

“…24,25 Mn 3 Ge, the compound of interest here, crystallizes in either the hexagonal D0 19 structure (e phase) or the tetragonal D0 22 structure (e 1 phase). The high-temperature hexagonal phase is obtained by annealing the material at 700 C, and quenching.…”