Boosting the Curie temperature in carbon-doped Mn₅Ge₃/Ge heterostructures
by A. Spiesser; M-T. Dau; L.A. Michez; M. Petit; C. Coudreau; A. Glachant; V. Le Thanh
International Journal of Nanotechnology (IJNT), Vol. 9, No. 3/4/5/6/7, 2012

Abstract: We have combined structural and magnetic characterisations to investigate the effect of carbon incorporation in epitaxial Mn₅Ge₃C_x films grown on Ge(111) by Molecular Beam Epitaxy (MBE). It is shown that up to a carbon content of saturation of ~0.6, most of carbon can be incorporated into the interstitial sites of the Mn₅Ge₃ lattice. Such a process results in a linear increase in the Curie temperature (T_C) of the alloy, which can reach a value as high as ∼430 K. Above this carbon content, T_C is found to decrease. Structural characterisations reveal that Mn₅Ge₃C_x films are in perfect epitaxy when x ∼0.6 whereas cluster formation in the grown layers is detected above that threshold. The clusters can be attributed to manganese carbide (MnC) compounds, which are formed when the carbon content exceeds the saturation value of 0.6 by consuming previously deposited carbon. In addition, we also show that after post-thermal annealing, the carbon-doped Mn₅Ge₃C_x alloys remain magnetically and structurally stable up to a temperature as high as 1123 K. The obtained results are very promising for integrating Mn₅Ge₃C_x into ferromagnetic/semiconductor heterostructures, the ultimate goal being the realisation of spintronics devices.

Online publication date: Mon, 06-Feb-2012

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