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The x-ray absorption and resonant inelastic x-ray spectra of iron pyrite (FeS2) have been measured at the S 2p edge and compared with published electronic structure calculations. A minimum in the x-ray absorption intensity interpreted as indicating a gap in the unoccupied density of states is found from about 4 to 6 eV above the bottom of the conduction band, in agreement with some recent calculations. Resonant Raman scattering conditions were set up at the onset of S 2p3/2 absorption and a constant energy loss peak at 1.9 eV was observed. This is assigned to transitions from occupied tg to unoccupied eg states, both of which are predominantly of Fe 3d character but hybridized with the S valence states. This demonstrates that Fe dd excitations can be probed via S 2p resonant spectroscopy, as has been done recently at the O 1s edge for oxide materials.

From a combination of NQR, NMR and AFNMR spectra in Cu1-xLixO information on the electric and magnetic electron-nucleus interactions is obtained. In particular, it is argued that Li+ enters the CuO lattice up to x approximately=4%, with a relatively small effect on the Neel temperature TN. 63Cu NQR and AFNMR, and 7Li NMR spin-lattice relaxation measurements are used to study the spin dynamics in the paramagnetic (PA) and in the antiferromagnetic (AF) phase and the effects associated with the creation of holes upon lithium doping. The Li doping modifies in a dramatic way the spin fluctuations in the AF phase. These effects are related to the fluctuations in the local Cu2+ spin configuration due to the diffusional motion of the extra holes in the electronic bands. A satisfactory explanation of the temperature and frequency dependences of Li relaxation rates is given in terms of a correlation time tau h for the hole motion controlled by an energy gap E(x) and quantitative information on tau h and E(x) are thus derived.

The electronic structure of the magnetic refrigerant Gd(5)Ge(2)Si(2) has been experimentally investigated by photoemission and x-ray absorption spectroscopy. The resonant photoemission and x-ray absorption measurements performed across the Gd N(4,5) and Gd M(4,5) edges identify the position of Gd 4f multiplet lines, and assess the 4f occupancy (4f(7)) and the character of the states close to the Fermi edge. The presence of Gd 5d states in the valence band suggests that an indirect 5d exchange mechanism underlies the magnetic interactions between Gd 4f moments in Gd(5)Ge(2)Si(2). From 175 to 300 K the first 4 eV of the valence band and the Gd partial density of states do not display clear variations. A significant change is instead detected in the photoemission spectra at higher binding energy, around 5.5 eV, likely associated to the variation of the bonding and antibonding Ge(Si) s bands across the phase transition.