Disappearance of Electron-Hole Asymmetry in Nanoparticles of Nd(1-x)CaxMnO3 (x = 0.6; 0.4): Magnetization and Electron Paramagnetic Resonance Evidence

TL;DR

This study reveals that nanoparticle forms of Nd(1-x)CaxMnO3 lose the electron-hole asymmetry observed in bulk, with similar magnetic behaviors and EPR characteristics, indicating size reduction significantly alters their electronic properties.

Contribution

It demonstrates that nanoparticle size reduces electron-hole asymmetry in Nd(1-x)CaxMnO3, evidenced by magnetic and EPR measurements showing similar behaviors in nano samples.

Findings

Nanoparticles lack charge ordering seen in bulk samples.

Magnetization behaviors of nano samples are similar despite different bulk properties.

EPR g-values converge in nano samples, indicating similar electronic environments.

Abstract

We study and compare magnetic and electron paramagnetic resonance behaviors of bulk and nanoparticles of Nd(1-x)CaxMnO3 in hole doped (x = 0.4;NCMOH) and electron doped (x = 0.6;NCMOE) samples. NCMOH in bulk form shows a complex temperature dependence of magnetization M(T), with a charge ordering (CO) transition at around 250 K, an antiferromagnetic (AFM) transition at around 150 K and a transition to a canted AFM phase/mixed phase at around 80 K. Bulk NCMOE behaves quite differently with just a charge ordering transition at around 280 K, thus providing a striking example of the so called electron-hole asymmetry. While our magnetization data on bulk samples are consistent with the earlier reports, the new results on the nanoparticles bring out drastic effects of size reduction. They show that M(T) behaviors of the two nano samples are essentially similar in addition to the absence of the charge order in them thus providing strong evidence for vanishing of the electron-hole asymmetry in nanomanganites. This conclusion is further corroborated by electron paramagnetic resonance studies which show that the large difference in the g-values and their temperature dependence found for the two bulk samples disappears as they approach a common behavior in the corresponding nano samples.