Critical behavior and magnetic relaxation dynamics of Nd0.4Sr0.6MnO3 nanoparticles

TL;DR

This study investigates the magnetic properties and critical behavior of Nd0.4Sr0.6MnO3 nanoparticles, revealing a size-induced ferromagnetic state, Griffiths-like phase, and complex relaxation dynamics distinct from bulk behavior.

Contribution

It provides detailed analysis of the magnetic phase transition, critical exponents, and relaxation phenomena in Nd0.4Sr0.6MnO3 nanoparticles, highlighting their unusual magnetic behavior and spin glass-like dynamics.

Findings

Nanoparticles exhibit ferromagnetic order unlike bulk antiferromagnetic behavior.

Presence of Griffiths-like phase in nanoparticles.

Nanoparticle dynamics best described by hierarchical spin glass model.

Abstract

Detailed dc and ac magnetic properties of chemically synthesized Nd0.4Sr0.6MnO3 with different particle size (down to 27 nm) have been studied in details. We have found ferromagnetic state in the nanoparticles, whereas, the bulk Nd0.4Sr0.6MnO3 is known to be an A-type antiferromagnet. A Griffiths-like phase has also been identified in the nanoparticles. Further, critical behavior of the nanoparticles has been studied around the second order ferromagnetic-paramagnetic transition region (|(T-TC)/TC|{\pounds} 0.04) in terms of modified Arrott plot, Kouvel-Fisher plot and critical isotherm analysis. The estimated critical exponents (b,g,d) are quite different from those predicted according to three-dimensional mean-field, Heisenberg and Ising models. This signifies a quite unusual nature of the size-induced ferromagnetic state in Nd0.4Sr0.6MnO3. The nanoparticles are found to be interacting and do not behave like ideal superparamagnet. Interestingly, we find spin glass like slow relaxation of magnetization, aging and memory effect in the nanometric samples. These phenomena have been attributed to very broad distribution of relaxation time as well as to inter-particle interaction. Experimentally, we have found out that the dynamics of the nanoparticle systems can be best described by hierarchical model of spin glasses.