Size and surface effects on the magnetic properties of NiO nanoparticles

Proença, Mariana P.; Sousa, C. T.; Pereira, A. M.; Tavares, Pedro B.; Ventura, J.; Vázquez, M.; Araújo, João P.

doi:10.1039/c1cp00036e

Cited by 143 publications

(93 citation statements)

References 42 publications

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“…On the other hand, the strain in the pure NiO powder is quite low and almost comparable to the NiO powder prepared by chemical preparation techniques. 27,28 However, the milled powder exhibits quite large strain, which increases with increasing the milling speeds. At larger milling speed, the strain also tends to saturate.…”

Section: Resultsmentioning

confidence: 99%

Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

2015

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We report systematic investigations of structural, vibrational, resonance and magnetic properties of nanoscale NiO powders prepared by ball milling process under different milling speeds for 30 hours of milling. Structural properties revealed that both pure NiO and as-milled NiO powders exhibit face centered cubic structure, but average crystallite size decreases to around 11 nm along with significant increase in strain with increasing milling speed. Vibrational properties show the enhancement in the intensity of one-phonon longitudinal optical (LO) band and disappearance of two-magnon band due to size reduction. In addition, two-phonon LO band exhibits red shift due to size-induced phonon confinement effect and surface relaxation. Pure NiO powder exhibit antiferromagnetic nature, which transforms into induced ferromagnetic after size reduction. The average magnetization at room temperature increases with decreasing the crystallite size and a maximum moment of 0.016 μB/f.u. at 12 kOe applied field and coercivity of 170 Oe were obtained for 30 hours milled NiO powders at 600 rotation per minute milling speed. The change in the magnetic properties is also supported by the vibrational properties. Thermomagnetization measurements at high temperature reveal a well-defined magnetic phase transition at high temperature (TC) around 780 K due to induced ferromagnetic phase. Electron paramagnetic resonance (EPR) studies reveal a good agreement between the EPR results and magnetic properties. The observed results are described on the basis of crystallite size variation, defect density, large strain, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion. The obtained results suggest that nanoscale NiO powders with high TC and moderate magnetic moment at room temperature with cubic structure would be useful to expedite for spintronic devices.

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Section: Resultsmentioning

confidence: 99%

Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

2015

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“…Extensive studies have been reported on particle size and morphology effects on magnetic properties of NiO prepared by various techniques, [7][8][9][10][11][12] but the results of the size effects on magnetic performance of NiO nanoparticles from different groups are inconsistent. 13,14 The inconsistent was considered due to the relatively large size distribution of particles with relatively irregular morphological.…”

Section: Introductionmentioning

confidence: 99%

Size-dependent magnetic properties of branchlike nickel oxide nanocrystals

Liú

Yang

2017

AIP Advances

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Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles AIP Advances 5, 087116 (2015) Branchlike nickel oxide nanocrystals with narrow size distribution are obtained by a solution growth method. The size-dependent of magnetic properties of the nickel oxides were investigated. The results of magnetic characterization indicate that the NiO nanocrystals with size below 12.8 nm show very weak ferromagnetic state at room temperature due to the uncompensated spins. Both of the average blocking temperature (T b ) and the irreversible temperature (T irr ) increase with the increase of nanoparticle sizes, while both the remnant magnetization and the coercivity at 300 K increase with the decrease of the particle sizes. Moreover, the disappearance of two-magnon (2M) band and redshift of one-phonon longitudinal (1LO) and two-phonon LO in vibrational properties due to size reduction are observed. Compared to the one with the spherical morphological, it is also found that nano-structured nickel oxides with the branchlike morphology have larger remnant magnetization and the coercivity at 5 K due to their larger surface-to-volume ratio and greater degree of broken symmetry at the surface or the higher proportion of broken bonds. © 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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“…The morphology, crystallography and size of the nano-structured materials can greatly influence their optical, electronic, magnetic, and catalytic properties [2]. Among transition metal oxides, nickel oxide (NiO) bulk and nano size have received considerable attention due to their wide range of applications in different fields, such as: catalysis [3], fuel cell electrodes and gas sensors [4], electrochromic films [5], battery cathodes [6], magnetic materials [7], and photovoltaic devices [8]. Because of the quantum size and surface effects, NiO nanoparticles exhibit catalytic, optical, electronic, and magnetic properties that are significantly different than those of bulk-sized NiO particles [9].…”

Section: Introductionmentioning

confidence: 99%