Relaxor behavior in manganites (invited)

The impurity (Cr3+)-doping effect on the stability of charge and orbital ordering has been systematically investigated for Nd1/2Ca1/2Mn1-yCryO3 crystals by measurements of magnetotransport and x-ray diffraction. The random field in terms of e(g) orbital deficiencies on the Cr sites drives the charge and orbital correlations to dynamical and short range, which is most relevant to the high-resistive state exhibiting colossal magnetoresistance. In the Cr-doped manganite, we can observe the coexistence of ferromagnetic-metallic and charge-orbital ordered phases, their spatial distributions, diffuse x-ray scattering, magnetic-field annealing, and the aging effect on the magnetic and electric properties, etc. These phenomena are reminiscent of those of relaxor ferroelectrics composed of ferroelectric clusters embedded in a paraelectric matrix. We propose that the mixed-valent manganite can be viewed as a "magneto- and electrorelaxor." (C) 2001 American Institute of Physics.