Am Dienstag den 04. Dezember setzt sich das IHT-Kolloquium fort, es spricht:
Prof. Dr. Lisa Michez
Maître de Conférences à Polytech-Marseille,
CINaM-CNRS, Marseille, Frankreich,
„Tuning the magnetic properties of Mn(5)Ge(3) by C Doping: How to Design a New Material for Spintronics Applications”
Much attention has been recently devoted to manganese germanides for their potential applications in spintronics devices. These materials that can be directly integrated into the silicon mainstream technologies represent indeed a new route to develop the beyond complementary metal-oxide-semiconductor technology. Among them, the Mn5Ge3 compound is particularly promising since it meets all the requirements for spin polarized transport.
However, the ferromagnetic order in Mn5Ge3 can be maintained only up to room temperature, which greatly hinders the use of this material for potential applications. We have recently demonstrated that the Curie temperature (TC) of this compound can be enhanced by incorporating a small amount of carbon into the Mn5Ge3 lattice. Theoretical calculations attribute this behavior to an enhancement of the Mn-Mn interactions mediated by C atoms placed in interstitial sites.
In this work, we have extensively studied the structural and magnetic properties of Mn5Ge3Cx films grown on Ge(111) by molecular beam epitaxy as a function of C concentration. Besides the compressive strain induced by the incorporation of C, the latter modifies significantly the Mn5Ge3 magnetic properties. Whereas Tc increases from 296K to 450K, the magnetocrystalline anisotropy in C-doped samples is reduced by nearly a factor 10 as x is increased from 0 to 0.7. This effect is assigned to hybridization between MnII and C atoms whose position has been investigated via EXAFS and STEM experiments. The magnetic properties of carbon-doped Mn5Ge3Cx thin films can therefore be tuned by adjusting the amount of C. This is very promising for the realization of spintronics devices and in addition, the presence of C is essential for the thermal stability and the high performances of Mn5Ge3 thin films.