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Rajeevan, N E,Kumar, Ravi,Shukla, D K,Thakur, P,Brookes, N B,Chae, K H,Choi, W K,Gautam, S,Arora, S K,Shvets, I V,Pradyumnan, P P IOP Pub 2009 Journal of physics, an Institute of Physics journa Vol.21 No.40
<P>We report the near-edge x-ray absorption spectroscopy (NEXAFS) at the Co/Mn L-3,L-2 edge and oxygen K edge of the well-characterized Bi-substituted Co2MnO4 multiferroic samples. The evolution of peak features in NEXAFS spectra of the Co/Mn L-3,L-2 edge and O K edge show the Bi-induced redistribution of magnetic cations (Co/Mn). The variation in valence states of Co and Mn in all the substituted compositions is consistent with the observed ferrimagnetic behaviour of the samples. Magnetization data show the decrease in molecular field complementing the ferrimagnetism. The role of Bi in the enhancement of magnetic interactions as well as the appearance of ferroelectricity in BixCo2-xMnO4 (0 <= x <= 0.3) is discussed.</P>
NEXAFS and XMCD studies of single-phase Co doped ZnO thin films
Singh, Abhinav Pratap,Kumar, Ravi,Thakur, P,Brookes, N B,Chae, K H,Choi, W K IOP Pub 2009 Journal of Physics, Condensed Matter Vol.21 No.18
<P>A study of the electronic structure and magnetic properties of Co doped ZnO thin films synthesized by ion implantation followed by swift heavy ion irradiation is presented using near-edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) measurements. The spectral features of NEXAFS at the Co L<SUB>3,2</SUB>-edge show entirely different features than that of metallic Co clusters and other Co oxide phases. The atomic multiplet calculations are performed to determine the valence state, symmetry and the crystal field splitting, which show that in the present system Co is in the 2+ state and substituted at the Zn site in tetrahedral symmetry with 10<I>Dq</I> = −0.6 eV. The ferromagnetic character of these materials is confirmed through XMCD spectra. To rule out the possibilities of defect induced magnetism, the results are compared with Ar annealed and Ar-ion implanted pure ZnO thin films. The presented results confirm the substitution of Co at the Zn site in the ZnO matrix, which is responsible for room temperature ferromagnetism.</P>
Evidence for the onset of color transparency in ρ<sup>0</sup> electroproduction off nuclei
CLAS Collaboration,El Fassi, L.,Zana, L.,Hafidi, K.,Holtrop, M.,Mustapha, B.,Brooks, W.K.,Hakobyan, H.,Zheng, X.,Adhikari, K.P.,Adikaram, D.,Aghasyan, M.,Amaryan, M.J.,Anghinolfi, M.,Arrington, J.,Ava North-Holland Pub. Co 2012 Physics letters: B Vol.712 No.4
We have measured the nuclear transparency of the incoherent diffractive A(e,e<SUP>'</SUP>ρ<SUP>0</SUP>) process in <SUP>12</SUP>C and <SUP>56</SUP>Fe targets relative to <SUP>2</SUP>H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced ρ<SUP>0</SUP>@?s on a nucleus relative to deuterium, which is sensitive to ρA interaction, was studied as function of the coherence length (l<SUB>c</SUB>), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q<SUP>2</SUP>). While the transparency for both <SUP>12</SUP>C and <SUP>56</SUP>Fe showed no l<SUB>c</SUB> dependence, a significant Q<SUP>2</SUP> dependence was measured, which is consistent with calculations that included the color transparency effects.