Interacting Superparamagnetism in La0.7Sr0.3MnO3 Nanoparticles

TL;DR

This study investigates the magnetic properties of La0.7Sr0.3MnO3 nanoparticles, revealing their superparamagnetic behavior, interactions, and size-dependent magnetization, with implications for nanoscale magnetic materials.

Contribution

It provides a detailed analysis of interacting superparamagnetism in La0.7Sr0.3MnO3 nanoparticles, including size estimation and core-shell magnetic structure modeling.

Findings

Nanoparticles exhibit superparamagnetism near room temperature.

Magnetic interactions are evidenced by Curie-Weiss behavior.

Particle size influences saturation magnetization, estimated below 15 nm.

Abstract

The magnetic order of La0.7Sr0.3MnO3 nanoparticles (NPs) fabricated in a SPEX D8000 mill was systematically studied. The La0.7Sr0.3MnO3 nanocrystals grow from the milled constituent oxides during the milling processes. The magnetization data obtained by using a SQUID magnetometer show the NPs as a superparamagnet in terms of anhysteretic curves near room temperature. Unoverlaping of the scaled M(H-ext, T)/M-s vs. H-ext, T plots and the dc susceptibility obeying the Curie-Weiss behavior rather than the Curie law at high temperatures provide evidence that the NPs are interacting superparamagnetic ensembles. A mean-field correction to the Langevin function L ([H-ext + alpha M]/k(B)T) worked well for the magnetic ordering of the NPs. By means of the Langevin fitting, the diameter of the NP was estimated to be lower than 15 nm, depending oil the milling time. The saturation magnetization of NPs varied from 48.5 em/g to 19 emu/g, with the higher value corresponding to a larger particle size. A core-shell structure of the NP was adopted, with the NP having the core-shell magnetically-effective mass density. This is applicable to the variation of the saturation magnetization with particle size.