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The electronic structures of the layered rare-earth chalcogenide compounds of CeTe2, PrTe2, and PrTe3, which have the charge-density wave (CDW) transition and possibly the chiral transition, have been investigated by employing soft X-ray absorption spectroscopy (XAS) and angle-resolved photoemission spectroscopy (ARPES). R 3d XAS measurements show that the valence states of Ce and Pr ions are nearly trivalent in all the compounds. Similar band dispersions are observed in their measured ARPES data, but with the band positions in PrTe3 being shifted up in energy compared to those in CeTe2 and PrTe2. These findings suggest that their Te 5p band structures are determined mainly by the 2D interactions in the Te(2)/Te(3) sheets, but with a larger number of holes in the Te 5p bands in PrTe3 than in CeTe2 and PrTe2. The measured constant energy maps of CeTe2, PrTe2, and PrTe3 for high binding energies are similar to one another, reflecting the Te 5p band structures of the Te(2)/Te(3) square nets. In contrast, the Fermi surfaces (FSs) of CeTe2 and PrTe3 exhibit extra features, different from the FS of the ideal Te(2)/Te(3) square nets, which arise from the CDW-induced FS reconstruction in the Te(2)/Te(3) sheets.

The electronic structures of multiferroic oxides of Ba(1-x)Bi(x)Ti(0.9)Fe(0.1)O(3) (0 < x < 0.12) have been investigated by employing photoemission spectroscopy and soft x-ray absorption spectroscopy (XAS). The measured Fe and Ti 2p XAS spectra show that Ti ions are in the Ti4+ states for all x and that Fe ions are Fe2+-Fe3+ mixed-valent for x > 0. The valence states of Fe ions are found to be nearly trivalent for x=0, and decreases with increasing x from being nearly trivalent (v(Fe)~ 3) for x=0 to v(Fe)~ 2.6 for x=0.12. The valence states of both Ti and Ba ions do not change for all x < 0.12. Based on the obtained valence states of Fe ions, the electronic and magnetic properties of Ba(1-x)Bi(x)Ti(0.9)Fe(0.1)O(3) are explored., 9 pages, 3 figures

Ca3CoXO6 (X = Co, Rh) is a low-dimensional system of materials with (CoXO6)∞ chains separated by Ca ions and packed in a triangular fashion. For Ca3Co2O6, each chain has CoO6 octahedra alternating with CoO6 trigonal prisms by sharing the triangular face; in the case of Ca3CoRhO6, most of the Co ions in the octahedral sites are replaced by Rh ions. We have studied Ca3CoXO6 (X = Co, Rh) by carrying out thorough measurements of its magnetic properties, high-resolution neutron powder diffraction, and X-ray absorption spectroscopy. Ferromagnetic ordering along the chain’s direction (c-axis) appears at T c1 ~ 25 K in Ca3Co2O6 while it occurs at a much higher temperature ~90 K in Ca3CoRhO6. The magnetic order in the packing ab-plane, which results from the interaction between neighboring ferromagnetic chains, is found to change from a partiallydisordered antiferromagnetic to a ferrimagnetic and then to a ferromagnetic one under an applied magnetic field in both Ca3Co2O6 and Ca3CoRhO6. For Ca3CoRhO6 with a higher T c1, a controllable parameter, that is, the degree of the Co-Rh cation site ordering exists within a chain, which affects the magnetic properties in a major way. This cation site order can be controlled experimentally by varying the rate of cooling to room temperature after the final sintering in the sample’s synthesis procedures. In the samples air-quenched at a cooling rate of several hundred K/min, T c1 was decreased to ~80 K from 90 K for normal samples with a 2-K/min cooling rate, and the ferrimagnetic region in the H -T phase diagram shrunk. In contrast, the Tc1 of the ones that were slow cooled at a cooling rate of ~0.5 K/min was increased to a higher temperature of ~100 K, and the ferrimagnetic region in the H - T phase diagram correspondingly became enlarged. For comparison, Ca3Co2O6 samples with different cooling rates were also investigated, and their magnetic properties were found to be independent of the synthesis conditions. We discuss the present results in terms of the disorder, frustration, and dimensionality of the Ca3CoXO6 system.

The electronic structures of molecule-based nanoparticles, such as biomineralized Helicobacter pylori ferritin (Hpf), Heme, and RbCo[Fe(CN)6]H2O (RbCoFe) Prussian blue analogue, have been investigated by employing photoemission spectroscopy and soft X-ray absorption spectroscopy. Fe ions are found to be nearly trivalent in Hpf and Heme nanoparticles, which provides evidence that the amount of magnetite (Fe3O4) should be negligible in the Hpf core and that the biomineralization of Fe oxides in the high-Fe-bound-state Hpf core arises from a hematite-like formation. On the other hand, Fe ions are nearly divalent and Co ions are Co2+-Co3+ mixed-valent in RbCoFe. Therefore this finding suggests that the mechanism of the photo-induced transition in RbCoFe Prussian blue analogue is not a simple spin-state transition of Fe2+-Co3+ → Fe3+-Co2+. It is likely that Co2+ ions have the high-spin configuration while Fe2+ ions have the low-spin configuration.

The electronic structures of Prussian blue analogue ACo[Fe(CN)6]H2O (A=Na, K) nano-size particles has been investigated by employing soft X-ray absorption spectroscopy (XAS) at the Fe and Co L edges. Both Fe and Co ions are found to be Fe2+-Fe3+ and Co2+-Co3+ mixed-valent, with the average valence of v(Fe)∼ 2.36 and v(Co)∼ 2.41. This finding suggests that the mechanism of the photo-induced spin transition in ACo[Fe(CN)6]H2O (A=Na, K) is not a simple spin-state transition of Fe2+-Co3+ → Fe3+-Co2+. The Fe ions in ACo[Fe(CN)6]H2O are also found to have a strong covalent bonding to (CN)− ligands, but a very weak bonding to O(H2O), while Co ions have a stronger bonding to O(H2O) than to (CN)− ligands.

Field Mapping System for the KIRAMS-30 Cyclotron Magnet K. H. Park, Y. D. Yoon, Y. G. Jung, D. E. Kim and B. K. Kang Pohang Accelerator Laboratory and Department of Electrical Engineering, Pohang University of Science and Technology, Pohang 790-784 J. Kang Cyclotron Application Laboratory, Korea Institute of Radiological and Medical Science, Seoul 139-706 J. S. Chai School of Information & Communication Engineering, Sungkyunkwan University, Suwon 440-764 (Received 12 August 2008, in nal form 5 December 2008) This paper presents a Hall-probe mapping system for measuring a cyclotron magnet. The system fabricated for the 30-MeV cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS). The Hall probes were mounted on a precision mechanical rotational stage and mapped the magnetic eld in a cylindrical coordinate system. The mapping system used the \ ying" mode eld mapping method to reduce the data-acquisition time. The time required for mapping the whole gap-area of the cyclotron magnet was 75 minutes. The relative random uctuation error during the entire mapping process was less than 0.01 %. The cyclotron magnet was corrected using the measured data for the magnetic eld. After the correction, the total phase excursion of the cyclotron was less than 12 , which is within the total phase excursion tolerance of 20 . PACS numbers: 41.20.-q

The electronic structure of the interface formation at Mn/Si at room temperature (RT) and the growth of manganese silicide were studied by using photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS) with synchrotron radiation. The Mn coverage dependence of the Si 2p and the Mn 3p core-level spectra revealed that the growth of Mn on Si(111)-7 × 7 at RT started in a layer-by-layer growth at a coverage of less than 0.5 ML (monolayer). Mn 2p XAS spectra also showed no reaction between Mn and Si at RT. Three thin manganese silicide samples were prepared by using solid phase epitaxy at 610 ◦C (MSS), reactive deposition epitaxy at 290 ◦C for Si(111) and at 350 ◦C for Si(100) (MSR) and post annealing the MSR sample at 610 ◦C (MSP) on the Si(111) and the Si(100) substrates. The LOW ENERGY ELECTRON DIFFRACTION (LEED) pattern and the fine structure in the Mn 2p XAS spectra showed that the phases of the MSS, the MSR, and the MSP samples were the same. Emissions at the Fermi energy in the valence-band (VB) PES spectra and the line shape of Si 2p core-level photoemission spectra also showed the formation of metallic MnSi.