We retract the paper [Appl. Phys. Express 2 (2009) 083002] that reported on the large tunnel magnetoresistance (TMR) in double-barrier magnetic tunnel junctions (DBMTJs) with a thin middle layer because an incorrect measurement system was used. We used a voltage/current-source/monitor (Advantest R6243) and connected it to the sample, as shown in Fig. 1. If (i) the central DBMTJ is in a state of electrical breakdown, (ii) the pads A and B have large resistance, and (iii) the source and the sense are connected through a protection circuit in R6243, the TMR effect of the two pads drastically enhances the TMR ratio. We apologize for the fact that the large TMR ratio of DBMTJs reported in our paper was artificially generated owing to the incorrect four-probe measurement.The authors wish to express gratitude to N. Suzuki of ADC Corporation for fruitful discussion of R6243 measurement system.

A series of fluorinated anatase TiO 2 nanosheets with dominant {001} facets were synthesized to oxidize pchlorophenol (PCP) and reduce Cr(VI) simultaneously under visible light. The {001}/{101} surface facets ratio of TiO 2 was controlled by varying the initial HF concentration, and fluorine-free samples were obtained by alkaline-washing. A synergistic effect among TiO 2 , Cr(VI), and PCP was observed, which is ascribed to effective trapping of photogenerated electrons and holes by Cr(VI) and PCP, respectively. A maximum synergistic effect was obtained at a molar ratio of [PCP] to [Cr(VI)] of one. Using X-ray diffraction, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer−Emmett−Teller analyses, the optimum ratio of exposed {001} to {101} facets for TiO 2 was determined to be 80:20 because of selective transfer and charge balance of photogenerated carriers. Surface fluorination facilitates the formation of oxygen vacancies and unsaturated Ti atoms, which is useful for visible light activity induction, extending the lifetime of photogenerated electron-hole pairs, and enhancing the rate of PCP oxidation and Cr(VI) reduction.

No abstract

No abstract