title: Correlation between the crystal structure and the Curie temperature in RCu3(Mn3Fe)O12 (R = rare-earth) complex perovskites.
abstract: New members of the family of complex-perovskite oxides with the formula RCu(3)(Mn(3)Fe)O(12) (R = Ce, Pr, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) have been synthesized and characterized. Polycrystalline samples have been prepared from citrate precursors treated under moderate pressure conditions (2-3.5 GPa) and 1000 °C in the presence of KClO(4) as an oxidizing agent. All the samples have been studied by neutron powder diffraction (NPD) at 300 K and 2 K. These oxides crystallize in the cubic space group Im3 (no. 204). Mn(4+)/Mn(3+) and Fe(3+) occupy at random the octahedral B positions of the perovskite structure. These materials have also been characterized by magnetic and magnetotransport measurements. The observed enhancement of T(C) along the RCu(3)(Mn(3)Fe)O(12) series is understood as an effect of the chemical pressure on the (Mn,Fe)-O bonds as R(3+) size decreases. The semiconducting behaviour observed in all of the samples is related with the introduction of Fe at B position. Despite the drastic change of the transport properties, significant negative magnetoresistance values are observed in the Fe-containing compounds both at 10 K and 300 K.
authors: Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid, Spain. paula.kayser@icmm.csic.es
authors: Paula
authors: P
authors: Kayser
authors: María Jesús
authors: MJ
authors: Martínez-Lope
authors: María
authors: M
authors: Retuerto
authors: Javier
authors: J
authors: Sánchez-Benítez
authors: María Teresa
authors: MT
authors: Fernández-Díaz
authors: José Antonio
authors: JA
authors: Alonso