Effects of Tb.sup.3+./sup. dopants in the La.sub.1-x./sub.Sr.sub.x./sub.MnO.sub.3./sub. bulk and nanoparticle ferromagnets

0461364 - FZÚ 2017 RIV GB eng J - Journal Article
Kaman, Ondřej - Hejtmánek, Jiří - Jirák, Zdeněk - Knížek, Karel - Maryško, Miroslav - Novák, Pavel - Vratislav, S.
Effects of Tb³⁺ dopants in the La_1-xSr_xMnO₃ bulk and nanoparticle ferromagnets.
Journal of Physics-Condensed Matter. Roč. 28, č. 20 (2016), 1-8, č. článku 206001. ISSN 0953-8984. E-ISSN 1361-648X
R&D Projects: GA ČR GA15-10088S
Institutional support: RVO:68378271
Keywords : crystal field splitting * Tb³⁺ ground states * neutron diffraction * ab initio calculations * perovskite manganite * nanoparticles
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 2.678, year: 2016

Three forms of La,Sr-manganites are synthesized and the role of Tb doping is investigated. First two systems are sol-gel nanoparticles and sintered ceramics of the composition La0.56Tb0.07Sr0.37MnO3, whereas the third system is formed by La0.51Tb0.06Sr0.43MnO3 synthesized in molten salt. The samples show pseudocubic perovskite structure with only small tilts of MnO6 that point to Ibmm symmetry in the bulk and R-3c symmetry in nanoparticles. SQUID magnetometry and neutron diffraction reveal a complete FM order of Mn spins in bulk, a reduced order in nanoparticles, and non-zero moments at A sites. Detailed analysis suggests that the dodecahedral coordination of A sites adapts to small terbium size, and the resulting crystal field splitting of Tb³⁺ yields a singlet ground state. The response to exchange and external fields is characterized as a giant Van Vleck paramagnetism in contrast to the Curie-type behaviour of Tb-based orthoaluminates and orthocobaltites.
Permanent Link: http://hdl.handle.net/11104/0261804