Magnetic exchange phenomena in reduced dimensions studied by neutron scattering

[Truncated abstract] This thesis deals with magnetic exchange interactions in thin lm magnetic materials focusing on phenomena related to intrinsic parameters of magnetic, structural and chemical order. In particular, the investigation is of two magnetic thin film systems, a Cu0.94Mn0.06/Co multilayer displaying a temperature-dependent magnetic ordering due to exchange coupling originating from dilute paramagnetic Mn spins, and thin films of chemical order modulated FePt3, showing a unique self-exchange bias effect. Detailed real-space models of the magnetic structure are obtained using polarized neutron reffectometry and high-angle neutron diffraction, speciffcally chosen to probe interface and bulk magnetic characteristics, respectively, in connection with complementary structural and magnetic characterization tools. It will be discussed, how the random distribution of dilute magnetic impurity centers in the Cu0.94Mn0.06/Co multilayers leads to a temperature-dependent interlayer exchange coupling with a strong biquadratic component. This manifests in an in-plane magnetic domain structure with a canted magnetization, i.e. a deviation from collinear alignments of external magnetic field and magnetization. The domain magnetizations show a high degree of vertical correlation in the form of columns throughout the multilayer, in which the sense of canting alternates in sign for each subsequent magnetic layer. Detailed analysis of temperature and field dependences of the magnetic structure lead to fundamental exchange energies, which are utilized in constructing a phenomenological model of exchange interactions between dilute magnetic impurities and the ferromagnetic layers.