Short-Range Magnon Excitation in NiO Nanoparticles

Gandhi, Ashish Chhaganlal; Pant, J.; Pandit, Swarada D.; Dalimbkar, Sunanda K.; Chan, Ting‐Shan; Cheng, C.Y; Ma, Yuan‐Ron; Wu, Sheng Yun

doi:10.1021/jp4029479

Cited by 87 publications

(70 citation statements)

References 48 publications

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“…The clustering makes an evaluation of the size distribution possible. A similar behavior of nanoparticle agglomeration has also been reported from NiO 21 , ZnO 22 nanoparticles, and NiO nanowalls 23 . However, the samples annealed at 800 °C (Fig.…”

Section: Resultssupporting

confidence: 80%

Role of cobalt cations in short range antiferromagnetic Co3O4 nanoparticles: a thermal treatment approach to affecting phonon and magnetic properties

Gawali

Gandhi

Gaikwad

et al. 2018

Sci Rep

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We report the phonon and magnetic properties of various well-stabilized Co3O4 nanoparticles. The net valence in cobalt (II)/(III) cation can be obtained by subtracting the Co2+ ions in tetrahedral interstices and Co3+ ions in the octahedral interstices, respectively, which will possess spatial inhomogeneity of its magnetic moment via Co2+ in tetrahedra and Co3+ in octahedral configurations in the normal spinel structure. Furthermore, the distribution of Co2+/Co3+ governed by various external (magnetic field and temperature) and internal (particle size and slightly distorted CoO6 octahedra) sources, have led to phenomena such as a large redshift of phonon-phonon interaction and short-range magnetic correlation in the inverse spinel structure. The outcome of our study is important in terms of the future development of magnetic semiconductor spintronic devices of Co3O4.

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Section: Resultssupporting

confidence: 80%

Role of cobalt cations in short range antiferromagnetic Co3O4 nanoparticles: a thermal treatment approach to affecting phonon and magnetic properties

Gawali

Gandhi

Gaikwad

et al. 2018

Sci Rep

Self Cite

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“…Vibration modes at around 400 cm 1 , 530 cm 1 , 730 cm 1 , 900 cm 1 , 1090 cm 1 , and 1450 cm 1 had been reported in the literatures and were attributed to one-phonon(1P) transverse optical (TO), (1P) longitudinal optical (LO), two-phonon (2P) TO, 2P TO+LO, 2P LO of vibrational origin and two-magnon (2M) band associated with Ni 2+ -O 2--Ni 2+ superexchange interaction, respectively. 5,14,20 And the 2M band, which supports the existence of antiferromagnetic (AFM) state through Ni 2+ -O 2--Ni 2+ superexchange interaction in bulk NiO, is not observed in this work. The disappearance of 2M intensity indicates that the decrease of AFM spin correlations.…”

Section: Resultsmentioning

confidence: 44%

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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“…This might be due to parity-breaking defects, since the concentration of vacancies is high as seen from the disappearance of 2M band in Raman scattering. 32,34 It may be noted that the perfect cubic and rhombohedral structured NiO does not show 1P LO scattering. 35 Furthermore, the peak position of 2P LO mode as shown in Figure 3(b) is shifted to lower wavenumber with decreasing size of the crystallites.…”

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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Short-Range Magnon Excitation in NiO Nanoparticles

Cited by 87 publications

References 48 publications

Role of cobalt cations in short range antiferromagnetic Co3O4 nanoparticles: a thermal treatment approach to affecting phonon and magnetic properties

Role of cobalt cations in short range antiferromagnetic Co3O4 nanoparticles: a thermal treatment approach to affecting phonon and magnetic properties

Size-dependent magnetic properties of branchlike nickel oxide nanocrystals

Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

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