Thickness and ordering temperature of surface NiO/Ni systems

Shih, Ying-Ta; Su, Chien-Yu; Tsai, Chieh-Yuan; Pan, W.

doi:10.1063/1.4866980

Cited by 4 publications

(3 citation statements)

References 31 publications

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“…These novel properties provide nanomaterials with a potential for technological applications such as magneto-recording, resistive switching, supercapacitors and biomedicine. [1][2][3][4][5][6] In particular, magnetic nanoparticles have been under scrutiny since the days of Néel 7 and Brown 8 who developed the theory of magnetization relaxation for non-interacting single domain particles. However, they show complex properties due to the occurrence of structural disorder, size distribution and random orientation of the magnetization vector, but majorly correlated to the interplay between finite size and surface effects.…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 99%

Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

2015

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“…What these simulations were unable to explain through Al 2 O 3 thickness and area variations is the spread in resistance data of each of the 4 and 5 nm thicknesses, where the 4 and 5 nm NiO diodes exhibited lower and higher resistance than expected from simulations, respectively. The spread in resistance values is attributed to a combination of thickness sensitive interfacial layer properties 18 , 19 and thickness-dependent NiO chemical composition (discussed in Supplementary Note 3 ).…”

Section: Resultsmentioning

confidence: 99%

Demonstration of resonant tunneling effects in metal-double-insulator-metal (MI2M) diodes

2021

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Although the effect of resonant tunneling in metal-double-insulator-metal (MI2M) diodes has been predicted for over two decades, no experimental demonstrations have been reported at the low voltages needed for energy harvesting rectenna applications. Using quantum-well engineering, we demonstrate the effects of resonant tunneling in a Ni/NiO/Al2O3/Cr/Au MI2M structures and achieve the usually mutually exclusive desired characteristics of low resistance ($${R}_{0}^{DC} \sim$$ R 0 D C ~ 13 kΩ for 0.035 μm2) and high responsivity (β0 = 0.5 A W−1) simultaneously. By varying the thickness of insulators to modify the depth and width of the MI2M quantum well, we show that resonant quasi-bound states can be reached at near zero-bias, where diodes self-bias when driven by antennas illuminated at 30 THz. We present an improvement in energy conversion efficiency by more than a factor of 100 over the current state-of-the-art, offering the possibility of engineering efficient energy harvesting rectennas.

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“…Since the discovery of exchange bias in the oxidized Co powders, the phenomenon has been intensively investigated for its potential applications in the spin valves, magnetic random access memory (MRAM), resistive switching, supercapacitors, and spintronics devices [1][2][3][4][5]. The phenomenon is arisen from the interface exchange coupling between ferromagnet and antiferromagnet [1].…”

Section: Introductionmentioning

confidence: 99%