Influence of Nd on the magnetic properties of Nd1-xCaxMnO3: an ESR study

The role played by the Nd ions in the magnetic properties of Nd0.5Ca0.5MnO3 and Nd0.7Ca0.3MnO3 is studied using static magnetization, neutron diffraction, and high frequency 9.4-475 GHz) electron spin resonance (ESR). We show that the Nd ions are weakly coupled to the Mn ions via ferromagnetic exchange and are responsible for the peculiar ferromagnetic resonance observed in the FM phase of both compounds (ground state below 120 K for x = 0.3, high field state for x = 0.5). We then use ESR to look for magnetic phase separation in the low field, charge order (CO) phase of Nd0.5Ca0.5MnO3. We show that there is no trace of the FM phase imbedded in the CO phase, contrary to what is observed in La0.5Ca0.5MnO3 or Pr0.5Sr0.5MnO3