Coercivity mechanism in hard magnetic SmCo₅/PrCo₅bilayers

Epitaxial SmCo 5 /PrCo y ( y = 5 and 8) films with PrCo y sublayers of varying thicknesses are prepared on a Cr buffered MgO(1 1 0) substrate by pulsed laser deposition, and their structural and magnetic properties are examined. These bilayer films grow epitaxially with a single orientation of the magnetic easy axis, which lies in the film plane along the MgO[0 0 1] direction. The intrinsic magnetic properties of the bilayers, such as the saturation polarization and anisotropy field, vary linearly with the relative PrCo y sublayer thickness. Surprisingly, coercivity shows a non-trivial dependence on the sublayer thickness and stacking order. This is discussed in a pinning dominated model and micromagnetic simulations are carried out to give an intriguing picture.