Germanium-based compounds have recently attracted considerable attention in Semiconductor Spintronics. The Mn5Ge3 compound have been grown on Ge(111) substrate so that epitaxial 'spin valves' can be fabricated. Recent experiments suggest a spin structure that is likely non-collinear. In order to gain deep insights into the magnetic structure of this compound, we have performed fully unconstrained ab-initio pseudo-potential calculations within spin density functional theory. We have considered several possible magnetic configurations: paramagnetic (PM), collinear (C) ferromagnetic (FM) and anti-ferromagnetic (AFM), non-collinear (NC) spin configurations. We first study the effect of the pressure. At equilibrium volume (V-eq = 0.203 nm(3)), the C-FM and NC self-consistent solutions (which have different magnetic states) are competing phases. For V similar or equal to 1.1 V-eq there is a crossover of the C-FM and C-ATM curves, with the C-AFM becoming favourite with respect to C-FM for larger volumes. Finally, we have studied the effect of strain field. Interestingly, the degeneracy of the NC phase with the C-spin configurations (FM and AFM) is definitely removed under the effect of uniaxial structural distortions (NC spin configuration is favoured under tensile uniaxial strain).
Competing magnetic phases of Mn5Ge3 compound
Peressi M
2007
Abstract
Germanium-based compounds have recently attracted considerable attention in Semiconductor Spintronics. The Mn5Ge3 compound have been grown on Ge(111) substrate so that epitaxial 'spin valves' can be fabricated. Recent experiments suggest a spin structure that is likely non-collinear. In order to gain deep insights into the magnetic structure of this compound, we have performed fully unconstrained ab-initio pseudo-potential calculations within spin density functional theory. We have considered several possible magnetic configurations: paramagnetic (PM), collinear (C) ferromagnetic (FM) and anti-ferromagnetic (AFM), non-collinear (NC) spin configurations. We first study the effect of the pressure. At equilibrium volume (V-eq = 0.203 nm(3)), the C-FM and NC self-consistent solutions (which have different magnetic states) are competing phases. For V similar or equal to 1.1 V-eq there is a crossover of the C-FM and C-ATM curves, with the C-AFM becoming favourite with respect to C-FM for larger volumes. Finally, we have studied the effect of strain field. Interestingly, the degeneracy of the NC phase with the C-spin configurations (FM and AFM) is definitely removed under the effect of uniaxial structural distortions (NC spin configuration is favoured under tensile uniaxial strain).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
