Magnetic relaxation phenomena and cluster glass properties of La0.7-xYxCa0.3MnO3 manganites -: art. no. 144404

The dynamic magnetic properties of the distorted perovskite system La0.7-xYxCa0.3MnO3 (0 less than or equal tox less than or equal to0.15) have been investigated by ac susceptibility and dc magnetization measurements, including relaxation and aging studies. All investigated samples display a metal-insulator transition. As yttrium is added in the compounds the overall results show evidence for the gradual appearance of a cluster glass behavior. For the x=0.15 sample, magnetization measurements as a function of time at various temperatures show that the magnetic relaxation is maximum at a given temperature, well below the ferromagnetic transition. This maximum coincides in temperature with a frequency-dependent feature in the imaginary part of the ac susceptibility, associated with a freezing process. This is interpreted as due to ferromagnetic clusters, which grow with decreasing temperature down to a temperature at which they freeze due to severe intercluster frustration.