X-ray spectroscopies are powerful tools for examining spin ordering phenomena in heterogenous materials. We present examples which highlight the key role of x-ray magnetic circular dichroism (XMCD) in investigating mixed valence oxides. First, we will introduce our recent observations on La_0:7Sr_0.3MnO₃ (LSMO) films grown on strontium titanate (STO). By using XMCD, we detected an unanticipated, “hidden” behavior in this typical wide bandwidth ferromagnet: the remanent magnetic state of the LSMO is reversed with respect to the direction of the applied magnetic field. We found that this hidden behavior is due to an inhomogeneous Mn 3d electron-distribution along surface normal direction, divided between an intermediate layer (enriched in Mn³⁺) and a nominal mixed-valence layer of LSMO. By controlling the applied field, film thickness, and/or temperature, we can generate different remanent states in a single LSMO film. Also, we will show that our findings offer considerable possibilities for application to thin-film devices, with potential for new forms of spin coupling and device functionality. Second, we will demonstrate how time-resolved XMCD, combined with ferromagnetic resonance (FMR), can be used to resolve spin dynamics to specifications and crystal field symmetries. Specifically, in a Mn-ferrite sample (nominal MnFe₂O₄ composition), we can resolve spin dynamics to Mn²⁺, Fe²⁺ and Fe³⁺ in octahedral and tetrahedral crystal fields. The results open up new possibilities for examining spin-lattice coupling mechanisms in oxide ferrimagnets.