Reorientational transition of the magnetic anisotropy in Co/Cr(001) superlattices

We have measured the magnetic anisotropy of Co/Cr(001) superlattices as a function of the Co thickness using magneto-optical methods and a torsion magnetometer. The samples grown by molecular-beam epitaxy exhibit a reorientational transition of the easy axis from in-plane for large Co thicknesses (tCo {≥} 15 {}) to out-of-plane for 10 {} {≤}tCo {≤} 15 {} and back again to the in-plane orientation for tCo {≤} 10 {} . We provide evidence that this reorientational transition of the magnetization direction is due to a sign change of the interface anisotropy constant induced by a concomitant structural phase transition of the Co layers from hcp to bcc with decreasing Co layer thickness. {} 1995 The American Physical Society.