Magnetic, structural and cation distribution studies on (x = 0.00, 0.02, 0.04, 0.06 and 0.1) nanoparticles

W. W. R. Araujo; J. F. D. F. Araujo; C. L. P. Oliveira; G. E. S. Brito; A. M. Figueiredo Neto

doi:10.1140/epje/i2019-11917-5

2024 Impact factor 2.2

Soft Matter and Biological Physics

Eur. Phys. J. E (2019) 42: 153
https://doi.org/10.1140/epje/i2019-11917-5

Regular Article

Magnetic, structural and cation distribution studies on $\mathrm{FeO}\cdot\mathrm{Fe}_{(2-x)}\mathrm{Nd}_{x} \mathrm{O_{3}}$ (x = 0.00, 0.02, 0.04, 0.06 and 0.1) nanoparticles

W. W. R. Araujo¹^*, J. F. D. F. Araujo², C. L. P. Oliveira¹, G. E. S. Brito¹ and A. M. Figueiredo Neto¹

¹ Institute of Physics, University of São Paulo, Rua do Matão 1371, 05508-090, São Paulo, SP, Brazil
² Department of Physics, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil

^* e-mail: wwlysses@gmail.com

Received: 20 August 2019
Accepted: 5 November 2019
Published online: 5 December 2019

Abstract

We synthesized and characterized the colloidal suspensions of $\mathrm{FeO}\cdot\mathrm{Fe}_{(2-x)}\mathrm{Nd}_{x} \mathrm{O_{3}}$ nanoparticles with x = 0.00, 0.02, 0.04, 0.06 and 0.1. The effect of the Fe³⁺ ion replacement by Nd³⁺ on the crystal structure is in-depth studied. The samples were characterized by the following techniques: X-ray diffraction (XRD), UV-Vis spectrophotometry, transmission electronic microscopy (TEM), small-angle X-ray scattering (SAXS), magnetization as a function of applied magnetic field (M-H loops) and magnetization as a function of temperature in zero-field-cooled and field-cooled regimes (ZFC-FC). From XRD cation distribution, structural parameters were extracted. The increasing in the bandgap is interpreted as a result of the higher interatomic separation with the doping. TEM micrographs reveal a polydisperse size and shape distribution of particles. The results for the volume-weighted average diameter measured by SAXS are consistent with those determined by XRD. From the M-H loops we found that the superparamagnetic (SPM) regime contributes with 95-97% for all samples, while only 3-5% contribution comes from the paramagnetic (PM) regime. The saturation magnetization increases in a steady manner upon increasing the Nd³⁺ ion molar ratio from 0.00 up to 0.06, reaching the maximum value of 105.8±0.4 Am²/kg at x = 0.06. It is worth to mention that the result for the saturation magnetization value are higher than that of the bulk material.