Neutron depolarisation in CoCr layers to study the perpendicular magnetic domain structure

Polarised neutrons (λ = 0.47 nm) are transmitted through sputtered CoCr films. From the measured diagonal elements of the depolarisation matrix it appears that the effective thickness heff of the films is about 50% of the actual thickness. When a soft magnetic NiFe film is deposited before or after deposition of the CoCr, heff, is 67 and 60% of the actual thickness, respectively, due to the disappearance of the flux closure in the CoCr film. From the angular dependence of the diagonal elements compared with computer simlation the “chain of column” model is supported. Our results indicate that magnetic flux is closed by “branched” spikes at least on the substrate side of the CoCr film.