X-ray absorption study of the Fe and Mo valence states in Sr2FeMoO6

We studied the Fe and Mo valence states in Sr2FeMoO6 using X-ray absorption spectroscopy. The exper- imental results were analyzed using atomic multiplet plus crystal field calculations. The analysis indi- cates that the Fe ions present a fairly ionic Fe3+ (3d5) valence, and that the Mo ions are in a strongly covalent Mo5+ (4d1) state. The presence of Fe ions in a 2+ valence state can be excluded from the Fe-L2,3 spectrum. These results can be understood taking into account the relative energy of the d-levels, the relative strength of the M d?O p mixing, and the exchange stabilization of the Fe3+ ion.Fil: Martins, H.P.. Universidade Federal Do Parana; BrasilFil: Prado, F.. Universidad Nacional del Sur; ArgentinaFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Vicentin, F.C. . Laboratório Nacional de Luz Síncrotron; BrasilFil: Chaves, D.S.. Laboratório Nacional de Luz Síncrotron; BrasilFil: Mossanek, R.J.O. . Universidade Federal Do Parana; BrasilFil: Abbate, M.. Universidade Federal Do Parana; Brasi

Bulk-sensitive Mo 4d electronic structure of Sr2FeMoO6 probed by high-energy Mo L3 resonant photoemission

We studied the Mo 4d electronic structure of Sr2FeMoO6 using high-energy Mo L 3 resonant photoemission. The experimental spectra are in good agreement with modified Becke-Johnson (mBJ) band structure calculations. The energy dependence of the spectra can be explained by the changes in the photoemission cross-sections. The Mo L 3 resonant spectrum shows Mo 4d character below the Fermi level and mixed Mo 4d-O 2p character around 8.0 eV. The Mo 4d weight in the resonant spectrum is in good agreement with the calculated interference between the direct and decay terms. The high photon energy used in this study (about 2520 eV) provides a bulk-sensitive determination of the Mo 4d electronic structure.Fil: Martins, H. P.. Universidade Federal do Paraná; BrasilFil: Prado, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vicentin, F.C.. Laboratorio Nacional de Luz Sıncrotron; BrasilFil: Mossanek, R. J. O.. Universidade Federal do Paraná; BrasilFil: Abbate, M.. Universidade Federal do Paraná; Brasi

Electronic Changes Related To The Metal-to-insulator Phase Transition In Rnio3

Rare earth nickel oxide perovskites (RNiO3, R=rare earth) have, except for LaNiO3, a metal-insulator (MI) phase transition as temperature decreases. The transition temperature (TMI) increases as the R-ion becomes smaller. They present also, at low temperatures, a complex antiferromagnetic order. For lighter R-ions (e.g. Pr and Nd), the antiferromagnetic transition temperature (TN) is close to TMI, while for heavier R-ions (e.g. Eu, Sm), TMI and TN are very far apart, suggesting that the magnetic and electronic behaviors are not directly coupled. Although RNiO3 perovskites are placed in the boundary of the Mott-Hubbard and charge transfer regimes, there are several evidences pointing to a charge transfer gap, mainly controlled by ligand-to-metal charge transfer energy, and thus strongly dependent on hybridization. Ni L-edge absorption spectroscopy (transition 2p → 3d) gives direct information on the density of Ni 3d empty states, and in particular on the multiplet splitting and hybridization between Ni3d and O2p bands. Here we present Ni L3 and L2 absorption spectra measured for NdNiO3 and EuNiO3 (TMI = 200 and 480 K). At room temperature, dramatic differences are observed between EuNiO3 (insulating) and NdNiO3 (metallic). The normalized spectra give evidence for a higher density of 3d unoccupied states and a larger multiplet splitting in EuNiO3. Both effects might be correlated to a decrease in hybridization. The same behavior is observed for NdNiO3 as it is cooled down to the insulating phase (T < 200 K), revealing that in these compounds the opening of the gap is directly related to the degree of hybridization.9211211125Lacorre, P., Torrance, J.B., Pannetier, J., Nazzal, A.I., Wang, P.W., Huang, T.C., (1991) J. Solid State Chem., 91, p. 225Torrance, J.B., Lacorre, P., Nazzal, A.I., Ansaldo, E.J., Niedermayer, Ch., (1992) Phys. Rev. B, 45, p. 8209Medarde, M.L., (1997) J. Phys. Cond. Matter, 9, p. 1679García-Muñoz, J.L., Rodríguez-Carvajal, J., Lacorre, P., (1992) Europhys. Lett., 20, p. 241García-Muñoz, J.L., Rodríguez-Carvajal, J., Lacorre, P., (1994) Phys. Rev. B, 50, p. 978Rodríguez-Carvajal, J., Rosenkranz, S., Medarde, M., Lacorre, P., Fernadez-Díaz, M.T., Fauth, F., Trounov, V., (1998) Phys. Rev. B, 57, p. 456Alonso, J.A., García-Muñoz, J.L., Fernández-Díaz, M.T., Aranda, M.A.G., Martínez-Lope, M.J., Casais, M.T., (1999) Phys. Rev. Lett., 82, p. 3871Alonso, J.A., Marínez-Lope, M.J., Casais, M.T., Aranda, M.A.G., Fernández-Díaz, M.T., (1999) J. Am. Chem. Soc., 121, p. 4754Alonso, J.A., Martínez-Lope, M.J., Casais, M.T., García-Muñoz, J.L., Fernández-Díaz, M.T., (2000) Phys. Rev. B, 61, p. 1756Medarde, M., Lacorre, P., Conder, K., Fauth, F., Furrer, A., (1998) Phys. Rev. Lett., 80, p. 2397Massa, N.E., Alonso, J.A., Martinez-Lope, M.J., Rasines, I., (1997) Phys. Rev., B56, p. 986Mroginski, M.A., Massa, N.E., Salva, H., Alonso, J.A., Martínez-Lope, M.J., (1999) Phys. Rev. B, 60, p. 5304De Groot, F.M.F., Puggle, J.C., Thole, B.T., Sawatzky, G.A., (1990) Phys. Rev. B, 42, p. 5459Zaanen, J., Sawatzky, G.A., Allen, J.W., (1995) Phys. Rev. Lett., 55, p. 418Mizokawa, T., Pujimori, A., Arima, T., Tokura, Y., Mori, N., Akimitsu, J., (1995) Phys. Rev. B, 52, p. 13865Medarde, M., Fontaine, A., García-Muñoz, J.L., Rodríguez-Carvajal, J., De Santis, M., Sacchi, M., Rossi, G., Lacorre, P., (1992) Phys. Rev. B, 46, p. 14975Alonso, J.A., Martinez-Lope, M.J., Hidalgo, M.A., (1995) J. Solid State Chem., 116, p. 146Abbate, M., Vicentin, F.C., Compagnon-Cailhol, V., Rocha, M.C., Tolentino, H., (1999) J. Synchrotron Rad., 6, p. 964De Groot, F.M.F., Fuggle, J., Thole, B.T., Sawatzky, G.A., (1990) Phys. Rev. B, 42, p. 545

30-day morbidity and mortality of sleeve gastrectomy, Roux-en-Y gastric bypass and one anastomosis gastric bypass: a propensity score-matched analysis of the GENEVA data

Background: There is a paucity of data comparing 30-day morbidity and mortality of sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), and one anastomosis gastric bypass (OAGB). This study aimed to compare the 30-day safety of SG, RYGB, and OAGB in propensity score-matched cohorts. Materials and methods: This analysis utilised data collected from the GENEVA study which was a multicentre observational cohort study of bariatric and metabolic surgery (BMS) in 185 centres across 42 countries between 01/05/2022 and 31/10/2020 during the Coronavirus Disease-2019 (COVID-19) pandemic. 30-day complications were categorised according to the Clavien–Dindo classification. Patients receiving SG, RYGB, or OAGB were propensity-matched according to baseline characteristics and 30-day complications were compared between groups. Results: In total, 6770 patients (SG 3983; OAGB 702; RYGB 2085) were included in this analysis. Prior to matching, RYGB was associated with highest 30-day complication rate (SG 5.8%; OAGB 7.5%; RYGB 8.0% (p = 0.006)). On multivariate regression modelling, Insulin-dependent type 2 diabetes mellitus and hypercholesterolaemia were associated with increased 30-day complications. Being a non-smoker was associated with reduced complication rates. When compared to SG as a reference category, RYGB, but not OAGB, was associated with an increased rate of 30-day complications. A total of 702 pairs of SG and OAGB were propensity score-matched. The complication rate in the SG group was 7.3% (n = 51) as compared to 7.5% (n = 53) in the OAGB group (p = 0.68). Similarly, 2085 pairs of SG and RYGB were propensity score-matched. The complication rate in the SG group was 6.1% (n = 127) as compared to 7.9% (n = 166) in the RYGB group (p = 0.09). And, 702 pairs of OAGB and RYGB were matched. The complication rate in both groups was the same at 7.5 % (n = 53; p = 0.07). Conclusions: This global study found no significant difference in the 30-day morbidity and mortality of SG, RYGB, and OAGB in propensity score-matched cohorts. © 2021, The Author(s)