Domains in CoCr investigated by neutron depolarization

Polarized neutrons (λ = 0.47 nm) are transmitted through RF and magnetron sputtered CoCr films (0.3-5 μm thick) with the polarization vector in the plane or perpendicular to the plane of the film. In the former case we can deduce from the depolarization the effective height h
eff
of the domains and from the angular dependence of the depolarization the section width δ (which is proportional to the domain width) in the remanent states after perpendicular and after in-plane saturation. As expected, h
eff
appears to be larger after perpendicular saturation and for a film thickness h ∼ 400 nm, h
eff
approaches h. This is attributed to the disappearance of reversed spike domains in the thinnest films. The lower h
eff
found in magnetron films with a lower surface/bulk coercivity ratio is also consistent with spike domain theory. The section width δ is found to he proportional to hx with x depending on the preparation or magnetic history of the film between 0.6 and 0.8. For magnetron films δ is ∼ 1.5 as large as in RF films of equal thickness, in qualitative agreement only with the fact that K
1
is twice as large as for RF films.