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NiO nanoparticles have garnered significant interest due to their diverse applications and unique properties, which differ markedly from their bulk counterparts. NiO nanoparticles are p-type semiconductors with a wide bandgap, high discharge capacity, and high carrier density, making them ideal for use in batteries, sensors, and catalysts. Their ability to generate reactive oxygen species also imparts disinfectant and antibiotic properties. Additionally, the higher Néel temperature of NiO compared with other antiferromagnetic materials makes it suitable for high-temperature applications in spintronic devices and industrial settings. This review focuses on the critical role of structure and composition in determining the magnetic properties of NiO nanoparticles. It examines how finite-size surface effects, morphology, crystallinity, and nickel distribution influence these properties. Fundamental physical properties and characterization techniques are discussed first. Various synthesis methods and their impact on NiO nanoparticle properties are then explored. Their magnetic phenomenology is examined in detail, highlighting the effects of finite size, particle composition and surface, and crystal quality. The review concludes with a summary of key insights and future research directions for optimizing NiO nanoparticles in technological applications. [ABSTRACT FROM AUTHOR]

The structural, electronic, magnetic, magnetocaloric, and thermoelectric properties of the SrXO3 (X = Mn and Fe) perovskite compounds were investigated using first-principles calculations. It was observed that the SrXO3 compounds are G-anti-ferromagnetic perovskites with partial magnetic moment with a value of 2.7 μ B and 2.4 μ B for Mn-3d and Fe-3d orbitals for SrMnO3 and SrFeO3, respectively. Moreover, by using Monte Carlo simulation (MCs) combined with the Metropolis algorithm, the calculated coupling interactions between the magnetic atoms Mn–Mn and Fe–Fe are J 1 Mn = 5. 1 7 meV and J 2 Mn = − 0. 6 meV for SrMnO3, J 1 Fe = 3. 4 4 meV and J 1 Fe = − 0. 4 meV for SrFeO3, respectively. Furthermore, a significant magnetocaloric effect (MCE) was observed around the Néel temperature of T N Mn = 2 6 0 K (for SrMnO3) and T N Fe = 1 3 4 K (for SrFeO3), and the maximal simulated magnetic entropy and relative cooling power values of all the studied compounds are found to be 100 J/kg (for SrMnO3) and 110 J/kg (for SrFeO3), respectively, with an applied magnetic field of H = 4. 0 T. These results are in complete agreement with the experimental results and more specifics than other theoretical calculations. Hence, SrXO3 compounds are considered promising candidates for magnetic refrigeration at low temperature. [ABSTRACT FROM AUTHOR]

We studied solid solutions of the system (1−x)PbFe1/2Nb1/2O3 - xPbFe2/3W1/3O3 using X-ray and Neuron diffraction, and Mössbauer spectroscopy. To obtain ceramics, we used the method of two-stage solid-phase synthesis and sintering according to the conventional ceramic technology. Pure solid solutions of the (1−x)PbFe1/2Nb1/2O3-xPbFe2/3W1/3O3 system were obtained. A deviation of the unit cell parameters from the Vegard rule was revealed, which indicates stratification of the structure into microregions differing in composition. The introduction of PbFe2/3W1/3O3 into the system led to partial ordering (clustering) of cations in the B position. An increase in magnetic moment with growing amount of PbFe2/3W1/3O3 was shown. [ABSTRACT FROM AUTHOR]

We studied solid solutions of the system (1−x)PbFe1/2Nb1/2O3 - xPbFe2/3W1/3O3 using X-ray and Neuron diffraction, and Mössbauer spectroscopy. To obtain ceramics, we used the method of two-stage solid-phase synthesis and sintering according to the conventional ceramic technology. Pure solid solutions of the (1−x)PbFe1/2Nb1/2O3-xPbFe2/3W1/3O3 system were obtained. A deviation of the unit cell parameters from the Vegard rule was revealed, which indicates stratification of the structure into microregions differing in composition. The introduction of PbFe2/3W1/3O3 into the system led to partial ordering (clustering) of cations in the B position. An increase in magnetic moment with growing amount of PbFe2/3W1/3O3 was shown. [ABSTRACT FROM AUTHOR]

In this work, nanocrystalline Sm 1-x R x FeO 3 (x = 0.0 and 0.5; R Pr, Nd, and Gd) samples have been synthesized via auto-combustion method and characterized to understand their microstructural, optical, electrical and multiferroic properties. X-ray diffraction data in combination with the FTIR spectra revealed the monophase and distorted orthorhombic configuration of all the samples with Pbnm space group. Rietveld refinement displayed a reduction in the bond length as well as the bond angle in the Sm 0.5 Gd 0.5 FeO 3 sample. Raman spectra exhibit compressive strain in Sm 0.5 Gd 0.5 FeO 3 nanoparticles; this finding is further supported by the XRD analysis. UV–visible spectroscopy manifests a reduction in the optical energy bandgap on moving Gd to Pr in Sm 0.5 R 0.5 FeO 3 system. Transmission electron microscopy (TEM) images in combination with energy dispersive x-ray (EDX) spectra reveal the non-uniform surface morphology with the agglomerated nature of nanoparticles and affirm the elemental compositions of all the samples. The room temperature P-E and M − H loops infer the multiferroic nature of all samples. Electron paramagnetic resonance (EPR) analysis divulges the weakening of the super-exchange interactions in Sm 0.5 R 0.5 FeO 3 system. DC electrical resistivity measurements reflect semiconductor-like behaviour in all prepared samples. The dielectric behaviour of the samples is in accordance with the "universal dielectric response" model. The temperature-dependent dielectric measurements of all prepared samples have been performed at 1 kHz to determine the Néel temperature (T N). The photocatalytic investigation depicts the superior photocatalytic response of Sm 0.5 Pr 0.5 FeO 3 nanoparticles under solar-light irradiation through the synergism of semiconductor-photocatalyzed oxidation and heterogeneous Fenton-like reaction. [ABSTRACT FROM AUTHOR]