CEQUINOR   05415
CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Crystal Structure, Magnetism, and Infrared Reflectivity of Double Perovskites Sr2BUO6 and Sr2BUO6¡d, B=Mn,Fe, Co, Ni, Zn
Autor/es:
R.M. PINACCA,; M. DEL C. VIOLA; J.C. PEDREGOSA; R.E. CARBONIO,; M.J. MARTINEZ-LOPE; J. A. ALONSO; F.P. DE LA CRUZ; N.E. MASSA
Lugar:
Baltimore, U.S.A.
Reunión:
Congreso; American Physical Society March Meeting; 2006
Institución organizadora:
American Physical Society
Resumen:
Double perovskites Sr2BUO6 where B´=Mn, Fe, Co, Ni, Zn have been prepared as a polycrystalline powder by solid- state reaction. and studied by X-ray di®raction and magnetic measurements. At 300K, they present the same monoclinic distorted crystal structure, space group P21 /n. The perovskite lattice consists of a completely ordered array of BO6 and UO6 octahedra exhibiting a slight tilting of the type a¡b+a¡. Magnetic measurements show antifer- romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. slight tilting of the type a¡b+a¡. Magnetic measurements show antifer- romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. of a completely ordered array of BO6 and UO6 octahedra exhibiting a slight tilting of the type a¡b+a¡. Magnetic measurements show antifer- romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. slight tilting of the type a¡b+a¡. Magnetic measurements show antifer- romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. B´=Mn, Fe, Co, Ni, Zn have been prepared as a polycrystalline powder by solid- state reaction. and studied by X-ray di®raction and magnetic measurements. At 300K, they present the same monoclinic distorted crystal structure, space group P21 /n. The perovskite lattice consists of a completely ordered array of BO6 and UO6 octahedra exhibiting a slight tilting of the type a¡b+a¡. Magnetic measurements show antifer- romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous compounds. slight tilting of the type a¡b+a¡. Magnetic measurements show antifer- romagnetism for the phases with B=Co, Ni and Mn at low temperature. The e®ective magnetic moment at T ¸ TNeel (5.22l B/f.u. for Co phase and 3.26 B/f.u. for Ni phase) suggests an unquenched orbital contribu- tion. The value for the Mn phase (5.74 B/f.u.) is consistent with that ex- pected for high-spin Mn2+ (5.91 B/f.u.). The topotactic reduction of the stoichiometric sample leads to oxygen de¯cient disordered perovskites, SrB0:5U0:5O3¡d having an orthorhombic distorted structure, space group Pbnm, at 300K. We will also comment on the temperature dependent infrared re°ectivity of Sr2CoUO6 and isomorphous com
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