Observation of Griffiths Phase in Polycrystalline ${\rm La}_{1-x}{\rm Ca}_{x}{\rm MnO}_{3}$ for $x\sim 0.20$

Polycrystalline samples La
_1-x
Ca
_x
MnO
₃
have been prepared by sol-gel method. X-ray diffraction patterns show that all the samples are mostly in single phase. Magnetic properties have been measured by Quantum Designed Physical Properties Measurement System. From the measured M - T curves, the samples show a traditional paramagnetic-to-ferromagnetic phase transition near Curie temperature. The Griffiths phase is found in all the samples from the temperature dependence curves of inverse susceptibility even for the samples with doping concentrations lower than 0.20 (the terminated doping concentration of Griffiths phase in single crystal La
_1-x
Ca
_x
MnO
₃
). A conclusion is summarized that the existence of Griffiths phase depends on whether the sample is single crystal or polycrystalline one.