Ferromagnetism in carbon-doped Mn5Si3 films

The effect of carbon doping on the structural and magnetic properties of Mn 5Si3Cx films is investigated for different substrate temperatures T-S and c oncentrations x. Samples with x approximate to 0.75 prepared at T-S=650-750 K exhibit ferromagnetic order with enhanced ordering temperatures T-C well above room temperature in contrast to the undoped antiferromagnetic Mn5Si3 compound. Structural analysis shows that C is incorporated interstitially in the hexagonal Mn5Si3-type structure with a lattice expansion with respec t to the undoped compound. The enhanced ferromagnetic order is presumably n ot simply due to a change of the interatomic Mn-Mn distances but due to a c hange of the electronic structure and/or exchange interactions. (C) 2000 Am erican Institute of Physics. [S0021-8979(00)91808-5].