  The influence of 30 keV He$^+$ ion irradiation on structural, electronic and
magnetic properties of Co$_2$MnSi thin films with B2 order was investigated. It
was found, that irradiation with light ions can improve the local chemical
order. This provokes changes of the electronic structure and element-specific
magnetization towards the bulk properties of the well-ordered Co$_2$MnSi
Heusler compound with L2$_1$ structure.
