Modeling magnetotransport in inhomogeneous (Ge,Mn) films
Résumé
We have performed numerical simulations using the finite elements method in order to investigate magnetotransport in manganese doped germanium thin films. Up to now, several groups have reported similar transport measurements on (Ge,Mn) films obtained either by low temperature molecular beam epitaxy or by manganese implantation of germanium wafers. However, different physical interpretations have been proposed, including the existence of a diluted carrier-mediated ferromagnetic phase. Here, by carefully taking into account the morphology of (Ge,Mn) films (Mn-rich ferromagnetic inclusions in a highly diluted germanium matrix), we can reproduce some experimental findings. In particular, in order to observe high positive magnetoresistance and Hall angles, there are two requirements: (i) a strong anomalous Hall effect within Mn-rich inclusions and (ii) a conductivity contrast between these inclusions and the germanium matrix. Finally, we conclude that (Ge,Mn) films behave as granular ferromagnetic systems.
Mots clés
semiconductor epitaxial layers
molecular beam epitaxial growth
magnetoresistance
Galvanomagnetic and other magnetotransport effects
semimagnetic semiconductors
semiconductor growth
electrical conductivity
ferromagnetic materials
finite element analysis
germanium
Hall effect
magnetic epitaxial layers
Elemental semiconductors
Nonmetallic ferromagnetic materials
Magnetic semiconductors
Molecular atomic ion and chemical beam epitaxy