Evolution from ferromagnetic order to cluster glass behavior in La0.7-xYxCa0.3MnO3 manganites

Magnetic measurements were performed on polycrystalline La0.7-xYxCa0.3MnO3, With x = 0, 0.07, 0.10 and 0.15. The shape of the field cooled and zero field cooled dc magnetization and the frequency dependence of the ac susceptibility are consistent with the appearance of a cluster-glass behavior in the higher Yttrium doped samples, Magnetic relaxation measurements also show a peak in the relaxation rate as the temperature is lowered below the ferromagnetic transition, due to the gradual formation of magnetic clusters. These results show that the magnetic phase diagram of manganese oxides, often plotted as a function of the average ionic radius of the A site, must include a cluster-glass-like ferromagnetic state.