Structural and magnetic stability of high energy ball milled Co2MnSi

• We studied the magnetic and structural properties of bulk and ball milled Co2MnSi.
• Structural disordering is minimal even at 36 nm.
• Constant value of TC shows strong ferromagnetic interaction in smaller particles.
• Formation of magnetically dead surface layer results reduction in magnetic moment.
• Variation of magnetic parameters is systematic with variation in milling time/size.

Structural and magnetic properties of ball milled Co2MnSi have been studied and compared with that of ordered bulk sample. The milled sample (with average size determined using the Williamson–Hall method) shows that the chemical ordering for this sample is very stable and is little effected by high energy ball milling. However, the reduction in the saturation magnetic moment of the milled sample shows that there is spin disordering induced on ball milling – attributable to the formation of a magnetically dead layer at the surface of the nano-sized samples. The ordered sample (unmilled) has a saturation moment value of 4.4 µB per formula unit at room temperature and is in agreement with the prediction of Slater Pauling curve. On milling it reduces to ~3 µB per formula unit at room temperature with an accompanying increase in the coercivity, retentivity and squareness factor.