And magnetic moments in highly correlated [Ce/La/Fe] and [La/Ce/Fe] multilayers studied by x-ray magnetic circular dichroism

Experiments are reported of x-ray absorption and x-ray magnetic circular dichroism at the (Formula presented) and (Formula presented) absorption edges of Ce and La in the multilayers [La/Ce(10Å)/La/Fe(30Å)](Formula presented) and [Ce/La(10Å)/Ce/Fe(30Å)](Formula presented). In these layers, Ce adopts an (Formula presented)-phase-like electronic structure. Strong (Formula presented) and (Formula presented) hybridization is effective at the interfaces. It induces an ordered magnetic moment on the (Formula presented) and (Formula presented) states in the ground state of Ce and of the (Formula presented) states of La at room temperature, in antiparallel orientation to the Fe moment. By choosing the special laminar structure of the two lanthanides intercalated in between the Fe layers, the spatial extension of the Fe-induced magnetic order is directly probed. The (Formula presented) polarization of Ce and the (Formula presented) polarization of La are limited to the direct interface with Fe. In contrast, the polarization of Ce-(Formula presented) states extends deeply into the layers. There is evidence that the (Formula presented) states of (Formula presented)-like Ce in these layered structures are very close to a ferromagnetic instability. Remarkably, magnetic order on the Ce-(Formula presented) states can exist without a polarization of the (Formula presented) states. Apparently the (Formula presented) hybridization wins over the intraatomic (Formula presented) exchange interaction, and stabilizes a nonmagnetic (Formula presented) ground state. Comparative studies on alloys Ce(Formula presented)Fe(Formula presented) confirm this observation: near (Formula presented) the polarization of the (Formula presented) states gets lost, but the (Formula presented) states are magnetically ordered. The special electronic and magnetic properties of Ce and La in the multilayer systems are reflected in the reversal of the macroscopic magnetization studied by the magneto-optical Kerr effect.