Activation Volumes in Co $_{2}$ FeSi Thin Films

Magnetic measurements and TEM analysis have been carried out in order to investigate the activation volume and its correlation with physical grain size within plasma sputtered Co₂FeSi thin films. This has led to a new technique for estimating the volumes of ordered and disordered interfacial regions within granular Heusler alloy films. It has been shown that the activation volume has very little grain-size dependence, while the physical grain volume is seen to increase with bias voltage. This suggests that reversal within the films is a domain wall process, and the multistage reversal seen in those films with larger grain sizes is due to pinning of domain walls within the grains.