The effect of phase separation on charge ordering state in La12xCaxMnO3 (x ¼ 1/2, 2/3, and 3/4)

The magnetic phase separation characteristics are found in manganese perovskite La1/3Ca2/3MnO3 by electron spin resonance (ESR) and magnetization measurements. An extra resonance signal observed in ESR spectra just above the charge ordering (CO) temperature TCO provides strong evidence for the existence of ferromagnetic (FM) clusters near the CO state. The investigation of the resistivity of La1-xCaxMnO3 (x=1/2, 2/3, and 3/4) in different magnetic fields up to 14 T shows that the effect of magnetic fields on CO state decreases with increasing x. Our results indicate that the percolative characteristics of the phase separation between FM clusters and CO state for x=1/2 and 2/3 samples are related to the magnetic field dependence of CO state. However, for x=3/4 it is assumed that there are no obvious FM clusters in the CO phase