Mixed magnetic behavior in gadolinium and ruthenium co-doped nickel oxide nanoparticles

Abstract

Pure and different concentrations from (Gd, Ru) co-doped NiO nanoparticles, capped with Polyvinylpyrrolidone (PVP), were fabricated by the co-precipitation method. The nanoparticles were characterized by different techniques. The Rietveld refinements of X-Ray Diffraction (XRD) patterns confirmed the formation of the pure face-centered-cubic NiO phase. The X-ray Photo-induced Spectroscopy (XPS) assured the trivalent oxidation state of the doped ions Gd3+ and Ru3+ and unveiled the multiple oxidation states of nickel ions (Ni2+ and Ni3+), emerging from the vacancies in the samples. The Transmission Electron Microscope (TEM) images showed the pseudospherical morphology of the samples and the Energy Dispersive X-ray permitted the quantitative analysis of the presented elements and their homogeneous distribution. The Raman and Fourier Transform Infra-Red (FTIR) spectra depicted the fundamental vibrational bands of NiO nanoparticles, confirming their purity. The UV-visible spectroscopy enabled the absorption measurements and the energy gap calculations. The co-dopants increased the energy bandgap of NiO nanoparticles from 3.15 eV for pure NiO to 3.62 eV with the highest concentration of the co-dopants (x = 0.02) The photoluminescence (PL) spectra gave insights into the possible defects present in the samples, such as nickel vacancies, single and double oxygen vacancies, and oxygen interstitials. The Vibrating Sample Magnetometer (VSM) studied the room temperature M-H loops of the co-doped samples. A combination of ferromagnetic, antiferromagnetic, and paramagnetic contributions was noticed and treated according to the law of approach to saturation and bound magnetic polaron (BMP) model. The magnetic parameters, such as the saturation magnetization, exchange and anisotropy field, and the BMP concentration were extracted from the fitted models and discussed in terms of the co-dopants’ concentration. The co-doped samples showed a softer magnetic behavior, which is recommended for data storage applications.

Structural, optical and magnetic properties of Ni1-2xMgxRuxO nanoparticles

“…In the second order phonon mode, the 2TO mode appears and the LO+TO mode disappears in the codoped samples. Similar appearance of the 2TO mode was observed in Raman spectra of (Gd, Ru) codoped NiO nanoparticles studied previously [13]. Also, a shifting in the 2LO mode can be noticed.…”

“…It's also reported that the main line, located at about 854 eV, arises from local screening effect, while its shoulder, located at about 856 eV, arises from non-local screening effect. The main peak undergoes a slight positive shift of ∼ 0.6 eV for x = 0.02 and ∼ 0.3 eV for x = 0.08, confirming the electronic interaction between the dopants with the Ni and is ascribed to the slight difference between their electronegativity [13]. The remaining satellite peaks appear as a result of the shake-up process due to the interaction of the photo-emitted 2p electrons with electrons in the d shell [44].…”

“…Additionally, the codopants increase the interparticle interactions, which causes morphological alterations and larger agglomeration [22]. the Ni 2+ oxidation state, while its shoulder, located at about 856 eV, is assigned to the Ni 3+ oxidation state [13,[41][42][43]. The area ratio of Ni 2+ /Ni 3+ is 0.386, 0.405 and 0.443 for x = 0, 0.02 and 0.08, respectively.…”

“…The dual doping process improved the crystallinity of NiO and increased its band gap energy. (REM, PGM) codoping of NiO was investigated by studying the effect of low codoping concentration of Gd and Ru on NiO [13]. Single-phase NiO was formed with Gd residing on the surface and Ru being incorporated into the lattice.…”

Impact of Mg-doping on the structural, optical, and magnetic properties of CuO nanoparticles and their antibiofilm activity

“…Hence, the reduction of the magnetocrystalline anisotropy with the increment of the non-magnetic Mg-dopants in the CuO lattice reduces the magnetostatic energy, which in turn reduces the coercivity [47]. The negligible retentivity and reduced coercivity for the synthesized Cu 1-x Mg x O nanoparticles render them magnetically clean materials recommended for data storage applications [47,48].…”