resumo
Using time-differential perturbed angular correlation of gamma rays, we investigated the electric-field gradient of polycrystalline EuTiO3 and Eu2Ti2O7, with Hf-181(Ta-181) as a probe, following different thermal treatments. The measurements were performed at ISOLDE-CERN following 80 keV implantation at the Bonn Radioisotope Separator. The experimental results indicated successful induction of different phases in the implantation recovery process at 1273 and 1373 K. These observations were combined with ab initio calculations and X-ray diffraction measurements. A comparison of ab initio calculated electric-field gradients with the measured values discriminates between different structures and defects and rules out many possible cases. The Ta probe at the Ti site in the Eu2Ti2O7 phase is found to be the most probable case of site occupation after annealing at 1373 K, while annealing at 1273 K keeps EuTiO3 in the vicinity of the Ta probe. A discussion of the hyperfine interactions that promote variation in the interaction strength at the Ta-181 site is presented.
palavras-chave
MAGNETIC-PROPERTIES; GRADIENT; CRYSTAL; TDPAC; PURE
categoria
Science & Technology - Other Topics; Materials Science; Physics
autores
Schell, J; Kamba, S; Kachlik, M; Maca, K; Drahokoupil, J; Rano, BR; Goncalves, JN; Dang, TT; Costa, A; Noll, C; Vianden, R; Lupascu, DC
nossos autores
João Nuno Santos Gonçalves
Investigador Júnioragradecimentos
This research has received funding from the Federal Ministry of Education and Research (BMBF) through Grant No. 05K16PGA. The authors also acknowledge the support of the Czech Science Foundation (Project Nos. 18-09265S and 17-05620S) and support from the Ministry of Education, Youth and Sports of the Czech Republic under Project Nos. CEITEC 2020 (LQ1601) and SOLID21 (CZ.02.1.01/0.0/0.0/16_019/0000760). We also acknowledge support from the Portuguese Foundation for Science and Technology (FCT) under Project No. CERN-FIS-NUC-0004-2015. The Danish Ministry of Higher Education and Science is thanked for financial support via the NICE grant. We thank J. G. M. Correia for technical assistance during these experiments and U. Koester for the irradiation at the Institut Laue-Langevin. We also thank V. V. Shvartsman for fruitful discussions.