Preparation and Structural Observation of Co₂MnSi Heusler Alloys by Mechanical Alloying

A Co₂MnSi Heusler alloy has been prepared by mechanical alloying (MA) method successfully using a mixture of elemental Co₅₀Mn₂₅Si₂₅ powders. A two-phase mixture of amorphous phase and remaining Mn were obtained after 5 hours of MA without any evidence for the formation of Co₂MnSi alloys. The saturation magnetization of MA powders decreased with MA time due to the magnetic dilution by alloying with nonmagnetic Mn and Si elements to 48 emu/g after 5 hours of MA. On the other hand, a Co₂MnSi single phase was obtained by MA after 3 hours and subsequently heat treated up to 650 °C. X-ray diffraction result showed that the average grain size of Co₂MnSi Heusler alloys prepared by MA for 5 hours and heat treatment to be in the range of 85 nm. The saturation magnetization of Co₂MnSi Heusler alloys prepared by MA and heat treatment reached a maximum value of 112 emu/g for 5 hours MA sample. It was also observed that the coercivity of 5 hours MA sample annealed at 650 °C was fairly low value of 27 Oe.