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Growth mechanism and magnon excitation in NiO nanowalls.

Gandhi AC, Huang CY, Yang CC, Chan TS, Cheng CL, Ma YR, Wu SY - Nanoscale Res Lett (2011)

Bottom Line: The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed.This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation.Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature.PACS: 75.47.Lx; 61.82.Rx; 75.50.Tt; 74.25.nd; 72.10.Di.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan. sywu@mail.ndhu.edu.tw.

ABSTRACT
The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed. The energy dispersive spectroscopy mapping technique was used to characterize the growth mechanism, and confocal Raman scattering was used to probe the antiferromagnetic exchange energy J2 between next-nearest-neighboring Ni ions in NiO nanowalls at various growth temperatures below the Neel temperature. This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation. Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature.PACS: 75.47.Lx; 61.82.Rx; 75.50.Tt; 74.25.nd; 72.10.Di.

No MeSH data available.


Related in: MedlinePlus

The simulation results using QS/QD versus temperature. Simulation results for the lattice diffusion theory for Ni atoms along the [1 1 1] plane, where short-circuit diffusion occurred at QS/QD to approximately one third. The dashed line represents the estimated length <S > obtained from the EDS mapping results at various TA.
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Figure 6: The simulation results using QS/QD versus temperature. Simulation results for the lattice diffusion theory for Ni atoms along the [1 1 1] plane, where short-circuit diffusion occurred at QS/QD to approximately one third. The dashed line represents the estimated length <S > obtained from the EDS mapping results at various TA.

Mentions: where β = 8 which is the number of positions a Ni atom can jump along the [111] plane; α = 0.2412 nm is the d-spacing of the [111] plane; D = 2 in the denominator is the two-dimensional constant; υD approximately 1012 per second is the vibration frequencya; τ is the growth time (approximately 10,800 s); QD = 59(1) kcal/mol is the activation energy of Ni [36]; and R (1.987 cal mol K-1) is the gas constant. The diffusion length of the NiO nanowalls is simulated based on the values of the lattice diffusion and various T and QS/QD, where QS is the short-circuit activation energy. The simulation results using QS/QD versus temperature are illustrated in Figure 6. The colored bar indicates the diffusion length, and the corresponding dash line indicates the diffusion length <S > obtained from EDS mapping. The QS/QD value of approximately 0.427(7) is higher than the short-circuit diffusion predicted QS/QD value of approximately one third at lower TA = 400°C, revealing that the growth of NiO grains is influenced by structural changes and strain between Ni and NiO. At higher TA, corresponding to our experimental data, the value of QS/QD is close to 0.32(2), indicating that short-circuit diffusion is the dominant transport mechanism in the oxidation of Ni, whether oxygen or nickel is the diffusion species along short-circuit path dislocations, resulting in the growth of NiO nanowalls at the higher temperature regime. Details related to the fitting parameters are listed in Table 3.


Growth mechanism and magnon excitation in NiO nanowalls.

Gandhi AC, Huang CY, Yang CC, Chan TS, Cheng CL, Ma YR, Wu SY - Nanoscale Res Lett (2011)

The simulation results using QS/QD versus temperature. Simulation results for the lattice diffusion theory for Ni atoms along the [1 1 1] plane, where short-circuit diffusion occurred at QS/QD to approximately one third. The dashed line represents the estimated length <S > obtained from the EDS mapping results at various TA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211999&req=5

Figure 6: The simulation results using QS/QD versus temperature. Simulation results for the lattice diffusion theory for Ni atoms along the [1 1 1] plane, where short-circuit diffusion occurred at QS/QD to approximately one third. The dashed line represents the estimated length <S > obtained from the EDS mapping results at various TA.
Mentions: where β = 8 which is the number of positions a Ni atom can jump along the [111] plane; α = 0.2412 nm is the d-spacing of the [111] plane; D = 2 in the denominator is the two-dimensional constant; υD approximately 1012 per second is the vibration frequencya; τ is the growth time (approximately 10,800 s); QD = 59(1) kcal/mol is the activation energy of Ni [36]; and R (1.987 cal mol K-1) is the gas constant. The diffusion length of the NiO nanowalls is simulated based on the values of the lattice diffusion and various T and QS/QD, where QS is the short-circuit activation energy. The simulation results using QS/QD versus temperature are illustrated in Figure 6. The colored bar indicates the diffusion length, and the corresponding dash line indicates the diffusion length <S > obtained from EDS mapping. The QS/QD value of approximately 0.427(7) is higher than the short-circuit diffusion predicted QS/QD value of approximately one third at lower TA = 400°C, revealing that the growth of NiO grains is influenced by structural changes and strain between Ni and NiO. At higher TA, corresponding to our experimental data, the value of QS/QD is close to 0.32(2), indicating that short-circuit diffusion is the dominant transport mechanism in the oxidation of Ni, whether oxygen or nickel is the diffusion species along short-circuit path dislocations, resulting in the growth of NiO nanowalls at the higher temperature regime. Details related to the fitting parameters are listed in Table 3.

Bottom Line: The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed.This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation.Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature.PACS: 75.47.Lx; 61.82.Rx; 75.50.Tt; 74.25.nd; 72.10.Di.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan. sywu@mail.ndhu.edu.tw.

ABSTRACT
The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed. The energy dispersive spectroscopy mapping technique was used to characterize the growth mechanism, and confocal Raman scattering was used to probe the antiferromagnetic exchange energy J2 between next-nearest-neighboring Ni ions in NiO nanowalls at various growth temperatures below the Neel temperature. This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation. Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature.PACS: 75.47.Lx; 61.82.Rx; 75.50.Tt; 74.25.nd; 72.10.Di.

No MeSH data available.


Related in: MedlinePlus