Zero-field La-139 nuclear magnetic resonance in La1-xCaxMnO3 for 0.125 <= x <= 0.5

Abstract

The zero-field La-139 nuclear magnetic resonance (NMR) was studied in polycrystalline La1-xCaxMnO3 for 0.125 less than or equal to x less than or equal to 0.5 to investigate magnetic phases in ordered states. The main result of this work is that mixed states are found near any phase transition boundary induced by either temperature or hole doping. The analysis of the NMR signal intensity and resonance frequency provides the evidence for ferromagentic clusters or magnetic polarons near the ferromagnetic transition temperature (T-C) The drastic change of the enhancement factor crossing the phase boundary at x = 0.2 implies the existence of single domain ferromagnetic microregions imbedded in an antiferromagnetic host for x<0.2. The comparison of NMR signal intensity with bulk magnetization shows that the macroscopic antiferromagnetic phase at x= 0.5 is a mixed state of microscopic ferromagnetic and antiferromagnetic phases. [S0163-1829(99)01801-9].