http://dspace-roma3.caspur.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Tue, 18 Jun 2013 06:05:36 GMT 2013-06-18T06:05:36Z http://dspace-roma3.caspur.it/image/logo_roma3.jpg http://dspace-roma3.caspur.it:80 http://hdl.handle.net/2307/64 <Title>Phase transitions in transition metal oxides studied by X-ray absorption spectroscopy</Title> <Authors>Monesi, Claudia</Authors> <Issue Date>2006</Issue Date> <Abstract>In this thesis is presented the study of three transition metal oxides, LaMnO3, CaMnO3 and Cr-doped V2O3</Abstract> Sat, 31 Dec 2005 23:00:00 GMT http://hdl.handle.net/2307/64 2005-12-31T23:00:00Z http://hdl.handle.net/2307/354 <Title>Antiferromagnetic-paramagnetic insulating transition in Cr-doped V2O3 investigated by EXAFS analysis</Title> <Authors>Meneghini, Carlo; Di Matteo, S.; Monesi, Claudia; Neisius, T.; Paolasini, L.; Mobilio, Settimio; Natoli, C. R.; Metcalf, P. A.; Honig, J. M.</Authors> <Issue Date>2009</Issue Date> <Is part of>Journal of Physics: condensed matter</Is part of> <Volume>21</Volume> <Pages>355401</Pages> <Abstract>We have performed extended x-ray absorption fine-structure (EXAFS) spectroscopy on a 2.8% Cr-doped V2O3 sample, with the aim of studying its structural evolution in a wide temperature range across the paramagnetic-antiferromagnetic insulating phase transition at T-c. The data were registered with two different set-ups in fluorescence and transmission geometries, for polarized and unpolarized spectra, respectively. Our idea, based on previous experiments reported in the literature, is that extended structural modifications of the nominal trigonal symmetry are present in the paramagnetic insulating phase for several tens of degrees above T-c, involving further-nearest-neighbor vanadium ions. Our data confirm that the paramagnetic insulating phase is not structurally homogeneous in a temperature range of about 30 K around T-c, where local distortions of monoclinic symmetry involving further-nearest neighbors are present. Moreover, the analysis of the absorption profile at Cr K-edge suggests that Cr ions enter the lattice randomly. We finally analyze our findings in light of current theoretical models.</Abstract> Wed, 31 Dec 2008 23:00:00 GMT http://hdl.handle.net/2307/354 2008-12-31T23:00:00Z