5.2 Coercivity dependence on the geometrical parameters

Due to its large saturation magnetization and relatively low magnetocrystalline anisotropy, the Fe films are ideal systems to observe the effects of antidots. In this section we will study the effects of the geometrical parameters in the coercivity in a square array of circular antidots on an Fe film. These parameters are the antidot diameter $ D$ and the interantidot distance $ \lambda $ (see Fig. 5.5). In the examined case the sides of the unit cell of the array are oriented parallel to the (1 1 0) Fe film directions, i.e. the unit cell diagonals are parallel to the Fe film crystallographic easy axes. In this geometry the easy axis of the induced anisotropy will coincide with the diagonals of the array square. The dipolar interaction prefer to separate the magnetic poles appearing on the surface. This is achieved aligning the magnetization with the diagonal of the array. Therefore, this geometry will produce a biaxial anisotropy that coincides in characteristics and disposition with the intrinsic Fe anisotropy. The thereinafter examined geometry is the one from the samples that were initially studied and measured by J.M. Torres as reported in his Ph.D. thesis [Torres 05].

Figure: Diagram representing the geometric parameters: antidot diameter $ D$ and interantidot distance $ \lambda $. In the graph the easy axis of the Fe biaxial anisotropy is also represented. The shape anisotropy easy axis corresponds also to the diagonals of the square formed by the antidots.