resumo
The crystal structure and magnetic ordering in NdBaCo(2)O(5+delta) cobaltites have been studied by neutron powder diffraction. A successful refinement of the high temperature paramagnetic patterns for both as-prepared (delta similar to 0.71) and oxidized (delta similar to 0.75) compositions was performed in the Pmmm space group with a 2a(p) X 2a(p) X 2ap unit cell. The symmetry relationships between this phase and other structural types observed in oxygen-deficient LBaCo(2)O(5+delta) perovskites are discussed. The analysis of the low-temperature diffraction data on oxidized NdBaCo(2)O(5.75) requires to account for the magnetic contribution originating from both the Nd and the Co sublattices. These are ordered at T(C)similar to 180 K and T(N)similar to 40 K, respectively, with ferromagnetic coupling inside the sublattices and antiferromagnetic coupling between them. A comparison of the neutron diffraction and magnetization data leads to the conclusion that no uniform ferromagnetic ordering of the Co sublattice is developed and a moderate amount of small antiferromagnetic clusters, exists below T(C).
palavras-chave
PHYSICAL-PROPERTIES; POWDER DIFFRACTION; PHASE-TRANSITIONS; SINGLE-CRYSTALS; OXYGEN-CONTENT; X-RAY; PRBACO2O5+DELTA; YBACO2O5+X; ANISOTROPY; ORDER
categoria
Physics
autores
Khalyavin, DD; Prokhnenko, O; Stusser, N; Sikolenko, V; Efimov, V; Salak, AN; Yaremchenko, AA; Kharton, VV
nossos autores
Aleksey Yaremchenko
Investigador Principal
Andrei Salak
Investigador Principal