Lattice disorder and Ferromagnetism in La0.67Ca0.33MnO3 nanoparticle

TL;DR

This study investigates how lattice disorder and particle size reduction in La0.67Ca0.33MnO3 nanoparticles influence their ferromagnetic properties, revealing a transition from first to second order phase change and enhanced magnetic irreversibility.

Contribution

It provides new insights into the effects of structural disorder and particle size on the magnetic phase transition and dynamics in La0.67Ca0.33MnO3 nanoparticles.

Findings

Decreased TC and MS with increased disorder

Change from first to second order phase transition

Distinct magnetic dynamics in amorphous vs nanocrystalline samples

Abstract

We study the ferromagnetism of La0.67Ca0.33MnO3 in bulk polycrystalline, nanocrystalline and amorphous phase. The structural change from crystalline phase to amorphous phase exhibited a systematic decrease of TC(paramagnetic to ferromagnetic transition temperature) and spontaneous magnetization (MS). The experimental results suggested few more features, e.g., appearance of large magnetic irreversibility in the temperature dependence of magnetization, lack of magnetic saturation at high magnetic field, blocking of magnetization below TB, and enhancement of coercivity. In addition, the magnetic phase transition near to TC has changed from first order character in bulk sample to second order character in nanocrystalline and amorphous samples. We understand the observed magnetic features as the effects of decreasing particle size and increasing magnetic (spin- lattice) disorder. We noted that magnetic dynamics of amorphous samples is distinctly different from the nanocrystalline samples. The ferromagnetism of amorphous samples are comparable with the properties of reported amorphous ferromagnetic nanoparticles. We also demonstrate the effect of disorder shell in controlling the dynamics of ferromagnetic cores.