Study of magnetization reversal in layered heterostructures by vector magnetometry

Multilayered films consisting of layer stacks with different anisotropies are studied by vector magnetometry i.e. simultaneous measurement of the components Mx, My along and perpendicular to the applied field respectively. The quantity Mx2+My2 is used as measure of the homogeneity of the reversal. For the [Co(6 Å)/Pt(15 Å)]4/(Pt(s))/[Co(10 Å)/Pt(15 Å)]4 with s = 0-45 Å series consisting of a perpendicular anisotropy bottom four-bilayer-stack coupled to a planar anisotropy top four-bilayer-stack a peak of the My component is clearly observed at the Mx coercivity. This is a sign of homogeneous reversal but it can be shown that similar effects can arise by decoupling of two layers with different (in-plane/perpendicular) anisotropies which is the case for s > 15 Å. In order to study the latter effect, a [Co(6 Å)/Pt(15 Å)]4/W(15 Å)/Co(24 Å) sample is used as a reference as it consists of a perpendicular anisotropy bottom four-bilayer-stack coupled to a vanishing anisotropy top Co layer through a W layer (which creates a magnetically inactive interface permitting only dipolar coupling). In contrast for [Co(5 Å)/Pt(10 Å)]6/Pt(s)/[Ni(15 Å)/Pt(5 Å)]6 series consisting of two different coercivity stacks which both have perpendicular anisotropy the decoupling does not manifest by appearance of peaks in the My component.