Search

Research was conducted to examine the environment of Er in epitaxial Ca1-xErxF2+x thin films using extended x-rays absorption fine structure and electron spin resonance studies at low temperatures. Film quality was compared with that of films grown by the molecular beam epitaxy method using photoluminescence experiments. Results indicate that the films are more convenient than the bulk materials to use in optical devices.

The magnetic and magnetoresistive properties of Ln(sub0.7)Pb(sub0.3)Mn(sub1-x)FexO(sub3) are reported. They were prepared using the sol-gel low temperature method which results in smaller grains, producing high purity and homogenous powders. The structural, magnetic, and magnetoresistance measurements were compared, to provide a better understanding of the effects due to the presence of different lanthanide elements and the substitution of Mn by Fe ions.

Pr1-xSrxFe0.8Ni0.2O3-δ (x=0.1, 0.2, and 0.3) polycrystalline phases were prepared by combustion synthesis. Their magnetic properties and Mössbauer effect have been examined in the range 5–300 K. Mössbauer spectroscopy shows the existence of charge disproportionation in several of the samples at low temperatures. Meanwhile, the samples present multiple features pointing out a frustrated magnetic order, with competing ferro- and antiferromagnetic interactions. Additionally, exchange bias (EB) phenomena have been observed. Hence, when the samples are cooled in a static magnetic field down to temperatures below 50 K, the hysteresis loops shift in the opposite direction to the applied biasing field, with shifts up to 10 kOe and more, and a small vertical shift of the loops also appears. This behavior seems linked to spin disorder and to the appearance of ferromagnetic (FM) ordered regions at low temperatures when cooling with a high applied field. The growth of these FM regions is likely due to the aligning role of an important cooling magnetic field over Ni-Fe and Fe5+-Fe3+ FM interactions. The higher FM contributions and therefore EB values found in the samples presenting charge disproportionation are related to the formation of FM regions in Fe5+-rich areas. [ABSTRACT FROM AUTHOR]

The article presents a complete magnetic, as well as structural characterization of the different thiol capped ferromagnetic Ag nanoparticles. The nanoparticles even with similar sizes are shown to exhibit different magnetic behaviors.

Different dodecanethiol capped Au nanoparticles (NP) with similar sizes but different ferromagnetic signals at room temperature are examined by using x-ray absorption spectroscopy at the Au [L.sub.3]-edge. The x-ray absorption near-edge structure (XANES) spectra have shown differences among the electronic structure of the Au NPs, which are compared with the different macroscopic magnetic signals.

The synthesis, structural study and Mossbauer spectroscopic and magnetic properties of the [Pr.sub.1-x][Sr.sub.x][Fe.sub.0.8][Ni.sub.0.2][O.sub.3-[delta]] (x

Reports on the 7Li and 31P nuclear magnetic resonance (NMR) analysis in the Li1-3xMgFexPO4 phases between 150 and 410 K. Methodology used to conduct the study; Information on the conductivity measurements performed; Details on the crystalline lithium compounds; Findings of the study.

Different dodecanethiol capped Au nanoparticles (NP) with similar sizes (∼2 nm) but different ferromagnetic signals at room temperature have been investigated by means of x-ray absorption spectroscopy at the Au L3-edge. The reversion of the x-ray magnetic circular dichroism signal with the change of sign of the external applied magnetic field confirms the location of the magnetism at the Au atoms. In comparison with the Au foil, all the samples present accentuated white lines at the x-ray absorption near-edge structure (XANES) indicating generation of 5d holes in the Au atoms located at surface of the NPs as consequence of a localized charge transfer from the Au surface atoms to the S atoms of the capping agent. XANES spectra reflect differences among the electronic structure of the Au NPs which are compared with the observed different macroscopic magnetic signals. [ABSTRACT FROM AUTHOR]