resumo
We report perturbed angular correlation measurements with Cd-111m/Cd-111 and In-111/Cd-111 probes, at the ISOLDE-CERN facility, in the manganite compounds BaMnO3, with the 6H and 15R polymorphs, and SrMnO3, with the 4H polymorph. The electric field gradient (EFG) is measured, and found approximately constant in a large temperature range for all the compounds. The EFG is also calculated from first principles with density functional theory, and compared with experimental results by considering diluted substitutional Cd impurities. Based on the results, we assign as sites for the probes the Ba (for BaMnO3-6H, 15R) and Sr (for SrMnO3-4H) sites, apart from fractions of undetermined origin in the case of BaMnO3-6H. We predict the hyperfine parameters in the recently synthesized multiferroic manganite Sr0.5Ba0.5MnO3, and its variation with the structure and electric polarization, which is found to be very small.
palavras-chave
CRYSTAL; FIELDS
categoria
Physics
autores
Goncalves, JN; Amaral, VS; Correia, JG; Lopes, AML; Araujo, JP; Tavares, PB
nossos autores
João Nuno Santos Gonçalves
Investigador
Vitor Brás Sequeira Amaral
Professor CatedráticoProjectos
MULTIFOX: Nanometric Probing and Modification of Multiferroic Oxides (PTDC/FIS/105416/2008)
Centre for Research in Ceramics and Composite Materials - CICECO (LA0011: 2011-2012) (PEst-C/CTM/LA0011/2011)
Centre for Research in Ceramics and Composite Materials - CICECO (LA0011: 2013-2014) (PEst-C/CTM/LA0011/2013)
agradecimentos
This work is supported by the program COMPETE/FFEDER and FCT under projects PTDC/FIS/105416/2008, CERN/ FP/123585/2011 and CICECO (PEst-C/CTM/LA0011/2011 and PEst-C/CTM/LA0011/2013). Further support from the ISOLDE collaboration, with approved project IS487, European Union Seventh Framework through ENSAR (contract no. 262010) and the BMBF German research program under contracts 05KK7TS2 and 05K10TS2 is acknowledged. JNG acknowledges his postdoctoral grant from FCT (SFRH/ BPD/82059/2011). We thank H Haas for useful discussions.