arXiv:1101.0238v1 [cond-mat.str-el]

We report an element-specific investigation of electronic and magnetic properties of the graphene/Ni(111) system. Using x-ray magnetic circular dichroism, the occurrence of an induced magnetism of the carbon atoms in the graphene layer is observed. We attribute this magnetic moment to the strong hybridization between C π and Ni 3d valence band states. The net magnetic moment of carbon in the graphene layer is estimated to be in the range of 0.05 − 0.1

In order to elucidate room-temperature ͑RT͒ ferromagnetism ͑FM͒ in ZnO, we have analyzed a multitude of experimental publications with respect to the ratio of grain-boundary ͑GB͒ area to grain volume. FM only appears if this ratio exceeds a certain threshold value s th . Based on these important results nanograined pure and Mn-doped ZnO films have been prepared, which reveal reproducible RT FM and magnetization proportional to the film thickness, even for pure ZnO films. Our findings strongly suggest that grain boundaries and related vacancies are the intrinsic origin for RT ferromagnetism.

A combined analysis of x-ray absorption and resonant reflectivity data was used to obtain the orbital polarization profiles of superlattices composed of four-unit-cell-thick layers of metallic LaNiO3 and layers of insulating RXO3 (R = La, Gd, Dy and X = Al, Ga, Sc), grown on substrates that impose either compressive or tensile strain. This superlattice geometry allowed us to partly separate the influence of epitaxial strain from interfacial effects controlled by the chemical composition of the insulating blocking layers. Our quantitative analysis reveal orbital polarizations up to 25 %. We further show that strain is the most effective control parameter, whereas the influence of the chemical composition of the blocking layers is comparatively small.