Magnetic phase diagram of Y1-xCaxMnO3

DINA TOBIA; ELIN WINKLER; JOSÉ VARGAS; MARÍA T. CAUSA; GABRIELA LEYVA; DANIEL VEGA

Reñaca, Chile

Workshop; VII Latin American Workshop on Magnetism, Magnetic Materials and their applications; 2005

In manganites A1-xBxMnO3 (A and B are, respectively, tri- and divalent ions) competing magnetic, electric and elastic interactions lead to very rich phase diagrams, which has been reported for several families of oxides ( with A = La, Pr, Nd; B = Ca, Sr). However, there are very few studies of compounds with smaller ionic radios (e.g. A = Y, Tb) where the perovskite structure is very distorted and is in the limit of stability. In this work we present a magnetization and ESR study of the orthorhombic Y1-xCaxMnO3 series with 0<=x<=1. The extreme compounds YMnO3 and CaMnO3 are G-type antiferromagnets with TN=44K and 123K respectively. Electron or hole doping introduce double exchange ferromagnetic (FM) interactions manifested mainly in the change of the Curie-Weiss temperature that become positive at 0.1<x<0.9. In the same range of doping, the obtained Curie constants deviate from the values expected for totally localized eg electrons. However long range FM ordering is never reached. For x<0.5 (hole doped samples) a spin glass transition at TSG~40K is observed. In the electron doped region instead, the samples are mainly AFM at low temperature, but with characteristics (localized polarons, charge ordering) that depend on x. We summarize our results in a phase diagram and compare it with the case of Tb1-xCaxMnO3, where non magnetic Y is replaced by magnetic Tb.