Inhomogeneous Cr concentration as origin of the perpendicular coercivity in Co-Cr films

Cr segregation at grain boundaries of columnar Co-Cr films as found by different authors may result in obstacles to domain wall motion or even in a breakdown of the exchange coupling between neighbouring grains. Both effects introduce an increase of the perpendicular coercivity. Its magnitude is estimated on the base of two different models: the wall-displacement model for exchange coupled grains and the model of rotational magnetization for exchange isolated columns. There is a satisfying agreement with experimental results for exchange coupled grains whereas the theoretical coercivities of exchange isolated columns are generally too high.