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89 results on '"Jang, Z."'

1. Dynamic effect of electron-number parity in metal nanoparticles

Author

Son, K., Park, D., Lee, C., Lascialfari, A., Yoon, S. H., Choi, K. Y., Reyes, A., Oh, J., Kim, M., Borsa, F., Scheutz, G., Yoon, Y. G., and Jang, Z. H.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Parity is a ubiquitous notion in science and serves as a fundamental principle for describing a physical system. Nanometer-scale metal objects are predicted to show dramatic differences in physical properties depending on the electron-number parity. However, the identification of the electron-number parity effects in real metal nanoparticles has remained elusive because of the variations in various features of nanoparticles. Here we report the nuclear magnetic resonance (NMR) detection of the dynamic effect of the electron-number parity in silver nanoparticles. With theoretical modeling of the NMR relaxation in silver nanoparticles, the measured nuclear spin-lattice relaxation rate is found to be proportional to the electron-number-parity-dependent susceptibility and to the temperature. This observation demonstrates the electron-number-parity-governed spin dynamics in silver nanoparticles., Comment: 52 pages, 16 figures

Published
2022

3. Putative spin liquid in the triangle-based iridate Ba$_3$IrTi$_2$O$_9$

Author

Lee, W. -J., Do, S. -H., Yoon, Sungwon, Lee, S., Choi, Y. S., Jang, D. J., Brando, M., Lee, M., Choi, E. S., Ji, S., Jang, Z. H., Suh, B. J., and Choi, K. -Y.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
Abstract

We report on thermodynamic, magnetization, and muon spin relaxation measurements of the strong spin-orbit coupled iridate Ba$_3$IrTi$_2$O$_9$, which constitutes a new frustration motif made up a mixture of edge- and corner-sharing triangles. In spite of strong antiferromagnetic exchange interaction of the order of 100~K, we find no hint for long-range magnetic order down to 23 mK. The magnetic specific heat data unveil the $T$-linear and -squared dependences at low temperatures below 1~K. At the respective temperatures, the zero-field muon spin relaxation features a persistent spin dynamics, indicative of unconventional low-energy excitations. A comparison to the $4d$ isostructural compound Ba$_3$RuTi$_2$O$_9$ suggests that a concerted interplay of compass-like magnetic interactions and frustrated geometry promotes a dynamically fluctuating state in a triangle-based iridate., Comment: Physical Review B accepted

Published
2017
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5. Proton NMR for Measuring Quantum-Level Crossing in the Magnetic Molecular Ring Fe10

Author

Julien, M. -H., Jang, Z. H., Lascialfari, A., Borsa, F., Horvatic, M., Caneschi, A., and Gatteschi, D.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The proton nuclear spin-lattice relaxation rate 1/T1 has been measured as a function of temperature and magnetic field (up to 15 T) in the molecular magnetic ring Fe10. Striking enhancement of 1/T1 is observed around magnetic field values corresponding to a crossing between the ground state and the excited states of the molecule. We propose that this is due to a cross-relaxation effect between the nuclear Zeeman reservoir and the reservoir of the Zeeman levels of the molecule. This effect provides a powerful tool to investigate quantum dynamical phenomena at level crossing., Comment: Four pages, to appear in Phys.Rev.Lett

Published
1999
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6. New band structures in Neutron-Rich Mo and Ru Isotopes

Author

Hamilton, JH, Luoa, YX, Zhu, SJ, Rasmussen, JO, Ramayya, AV, Goodin, C, Li, K, Hwang, JK, Liu, S, Almehed, D, Frauendorf, S, Dimitrov, V, Zhang, JY, Che, XL, Jang, Z, Stefanescu, I, Gelberg, A, Ter-Akopian, GM, Daniel, AV, Lee, IY, Ding, HB, Xu, RQ, Wang, JG, Xu, Q, Stoyer, MA, Donangelo, R, and Stone, NJ

Subjects
Nuclear & Particles Physics, Mathematical Sciences, Physical Sciences
Abstract

Rotational bands in 110,112Ru and 108Mo have been investigated by means of γ-γ-γ and γ-γ(θ) coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf. New δI = 1 negative parity doublet bands are found. These bands in 110,112Ru and 108Mo have all the properties expected for chiral vibrations. Microscopic calculations that combine the TAC meanfield with random phase approximation support this interpretation.

Published
2009

7. Hierarchically Skeletal Multi-layered Pt-Ni Nanocrystals for Highly Efficient Oxygen Reduction and Methanol Oxidation Reactions

Author

Li, S., Tian, Z. Q., Liu, Y., Jang, Z., Hasan, S. W., Chen, X., Tsiakaras, P., and Shen, P. K.

Subjects
ELECTROCATALYSTS, BINARY ALLOYS, HIERARCHICAL STRUCTURES, BRANCHED NANOCRYSTALS, PLATINUM ALLOYS, HIERARCHICALLY SKELETAL PT-NI NANOCRYSTALS, METHANOL OXIDATION REACTION, INORGANIC ACIDS, OXYGEN, FUEL CELLS, SOLVENT THERMAL METHOD, SOLVOTHERMAL METHOD, ELECTROLYTIC REDUCTION, NANOCRYSTALS, OXYGEN REDUCTION REACTION, NICKEL ALLOYS, INTRINSIC ACTIVITIES, METHANOL OXIDATION REACTIONS, METHANOL, ELECTROCHEMICAL SURFACE AREA, ACTIVITY, REVERSIBLE HYDROGEN ELECTRODES, SELF-ASSEMBLY, MULTI-LAYERED STRUCTURE
Abstract

Pt based materials are the most efficient electrocatalysts for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in fuel cells. Maximizing the utilization of Pt based materials by modulating their morphologies to expose more active sites is a fundamental objective for the practical application of fuel cells. Herein, we report a new class of hierarchically skeletal Pt-Ni nanocrystals (HSNs) with a multi-layered structure, prepared by an inorganic acid-induced solvothermal method. The addition of H2SO4 to the synthetic protocol provides a critical trigger for the successful growth of Pt-Ni nanocrystals with the desired structure. The Pt-Ni HSNs synthesized by this method exhibit enhanced mass activity of 1.25 A mgpt−1 at 0.9 V (versus the reversible hydrogen electrode) towards ORR in 0.1-M HClO4, which is superior to that of Pt-Ni multi-branched nanocrystals obtained by the same method in the absence of inorganic acid; it is additionally 8.9-fold higher than that of the commercial Pt/C catalyst. Meanwhile, it displays enhanced stability, with only 21.6% mass activity loss after 10,000 cycles (0.6–1.0 V) for ORR. Furthermore, the Pt-Ni HSNs show enhanced activity and anti-toxic ability in CO for MOR. The superb activity of the Pt-Ni HSNs for ORR and MOR is fully attributed to an extensively exposed electrochemical surface area and high intrinsic activity, induced by strain effects, provided by the unique hierarchically skeletal alloy structure. The novel open and hierarchical structure of Pt-Ni alloy provides a promising approach for significant improvements of the activity of Pt based alloy electrocatalysts. © 2021 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences. This work was supported by the National Key Research and Development Plan (2017YFB0103001), the link project of the National Natural Science Foundation of China and Fujian Province (U1705252), the Guangxi Science and Technology Projects (AA17204083, AB16380030), the innovation project of Guangxi Graduate Education (YCBZ2019012).

Published
2021

14. Putative spin liquid in the triangle-based iridate Ba3IrTi2O9

Author

Lee, W.-J., primary, Do, S.-H., additional, Yoon, Sungwon, additional, Lee, S., additional, Choi, Y. S., additional, Jang, D. J., additional, Brando, M., additional, Lee, M., additional, Choi, E. S., additional, Ji, S., additional, Jang, Z. H., additional, Suh, B. J., additional, and Choi, K.-Y., additional

Published
2017
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15. Spin decoherence processes in the S=1/2 scalene triangular cluster (Cu3(OH))

Author

Ponomaryov, A. N., Kim, N., Jang, Z. H., Tol, J., Koo, H.-J., Law, J. M., Suh, B. J., Yoon, S., and Choi, K. Y.

Abstract

We report the synthesis and magnetic properties of the molecular cluster Cu3(μ3−OH)(μ-OH)(μ-O2Ar4F-Ph)2(py)3(OTf)2, abbreviated as (Cu3(OH)). Using magnetization, electron paramagnetic resonance and spin dimer analysis, we derive a microscopic magnetic model of (Cu3(OH)) and measure the electron T1 and T2 relaxation times. The Cu2+ ions are arranged to form a distorted triangular structure with the three different exchange coupling constants J1 = −43.5 K, J2 = −53.0 K, and J3 = −37.7 K. At T = 1.5 K T1 is of the order of 10−4 s and T2 is evaluated to be 0.26 μs. We find that the temperature dependence of 1/T1 and 1/T2 is governed by Orbach process and spin bath fluctuations, respectively. We discuss the role of spin–phonon mechanism in determining a spin decoherence time in a class of spin triangular clusters.

Published
2015

16. Magnetic properties of artificially synthesized ferritins.

Author

Kim, B. J., Lee, H. I., Cho, S. -B., Yoon, S., Suh, B. J., Jang, Z. H., Pierre, T. G. St., Kim, S. -W., and Kim, K. -S.

Abstract

Human ferritin homopolymers with H or L subunits (rHF and rLF) were genetically engineered in E coli. Apoferritins were then reconstituted with 2000 Fe atoms. A big difference was observed in the rates of iron uptake, whereas the mean core size was similar in rHF and rLF. Magnetization of the recombinant human ferritins were measured as functions of temperature and field. The blocking temperature TB(H) at low fields is considerably higher in rLF than in rHF. From the fit of M(H) data to a modified Langevin function: M(H)=M0L(μpH/kBT)+χaH, the effective magnetic moment μp is found to be much larger in rLF than in rHF. Experimental data demonstrate that the magnetic properties, in particular, the uncompensated spins of ferritin core are related to the biomineralization process in ferritins. [ABSTRACT FROM AUTHOR]

Published
2005
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17. [sup 1]H and [sup 23]Na nuclear magnetic resonance study of V6 magnetic molecular clusters.

Author

Jung, J. K., Procissi, D., Jang, Z. H., Suh, B. J., Borsa, F., Luban, M., Ko¨gerler, P., and Mu¨ller, A.

Subjects
MICROCLUSTERS, NUCLEAR magnetic resonance
Abstract

We report ¹H and [sup 23]Na nuclear magnetic resonance (NMR) and relaxation measurements in two variants of the V6 cluster with formula [CH[sub 3]H[sub 6][sub 4]Na[sub 2][H[sub 4]{V[sub 3]L}[sub 2]P[sub 4]O[sub 4]]·14H[sub 2]O and Na[sub 6][H[sub 4]{V[sub 3]L}[sub 2]P[sub 4]O[sub 4]]· 18H[sub 2]O, respectively. Both the NMR linewidth and the spin-lattice relaxation (NSLR) data can be explained semiquantitatively by assuming a dipolar coupling between the proton (sodium) nuclei and the three V(IV) magnetic moments forming an almost equilateral triangle with nearest neighbor antiferromagnetic exchange interactions. From the temperature dependence of the [sup 23]Na NSLR we obtain the value of the two gaps separating the lower energy total spin states. [ABSTRACT FROM AUTHOR]

Published
2002
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18. Proton spin-lattice relaxation at low temperature in the ferromagnetic spin ring Cu6.

Author

Furukawa, Y., Lascialfari, A., Jang, Z. H., and Borsa, F.

Subjects
SPIN-lattice relaxation, NUCLEAR magnetic resonance, FERROMAGNETIC materials
Abstract

We report [sup 1]H nuclear magnetic resonance spin-lattice relaxation rate (NSLR) measurements as a function of temperature (1.5–4.2 K) and as a function of applied magnetic field (0.2–8.2 T) in the molecular magnet [(PhSiO[sub 2])[sub 6]Cu[sub 6](O[sub 2]SiPh)[sub 6]] in short Cu6. The results are explained in terms of a simple model whereby the NSLR is driven by the fluctuations of the local hyperfine field due to the reorientation of the total spin of the molecule in its ground state. From the analysis of the data, we infer the temperature and field dependence of the characteristic rate of the fluctuations of the total magnetization of the Cu6 ring in its ground state. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2000
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20. Evolution of chirality from gamma Soft Ru-108 to triaxial Ru-110,Ru-112

Author

Luo, YX, Zhu, SJ, Hamilton, JH, Rasmussen, JO, Ramayya, AV, Goodin, C, Hwang, JK, Almehed, D, Frauendorf, S, Dimitrov, V, Zhang, Jing-ye, Che, XL, Jang, Z, Stefanescu, Irina, Gelberg, A, Ter-Akopian, GM, Daniel, AV, Stoyer, MA, Donangelo, R, Cole, JD, and Stone, NJ

Subjects
vibrations, spectroscopy, ru-108,ru-110,ru-112, Spontaneous fission of 252Cf, bands, nuclei, 108,110,112Ru, fission, Chiral vibration, spontaneous fission of cf-252, isotopes
Abstract

Rotational bands in Ru-108,Ru-110,Ru-112 have been investigated by means of gamma-gamma-gamma and gamma-gamma(theta) coincidences of prompt gamma rays emitted in the spontaneous fission of Cf-252. The positive parity bands are described by different versions of IBA, where Ru-108 is best described as a gamma-soft nucleus whereas Ru-110,Ru-112 these are more like rigid triaxial rotors. New Delta I = 1 negative parity doublet bands are found. In case of Ru-110,Ru-112, these are interpreted as soft chiral vibrations. Many of the experimental findings can be explained by microscopic calculations that combine the TAC mean-field with random phase approximation but a simple geometrical explanation is not apparent. ispartof: Physics letters b vol:670 issue:4 pages:307-312 status: published

Published
2009

29. Evolution of chirality from γ soft 108Ru to triaxial 110,112Ru

Author

Luo, Y.X., primary, Zhu, S.J., additional, Hamilton, J.H., additional, Rasmussen, J.O., additional, Ramayya, A.V., additional, Goodin, C., additional, Li, K., additional, Hwang, J.K., additional, Almehed, D., additional, Frauendorf, S., additional, Dimitrov, V., additional, Zhang, Jing-ye, additional, Che, X.L., additional, Jang, Z., additional, Stefanescu, I., additional, Gelberg, A., additional, Ter-Akopian, G.M., additional, Daniel, A.V., additional, Stoyer, M.A., additional, Donangelo, R., additional, Cole, J.D., additional, and Stone, N.J., additional

Published
2009
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31. EVIDENCE FOR CHIRAL DOUBLET BANDS IN 110,112Ru

Author

LUO, Y.X., primary, ZHU, S.J., additional, HAMILTON, J.H., additional, RASMUSSEN, J.O., additional, RAMAYYA, A.V., additional, GOODIN, C., additional, LI, K., additional, HWANG, J.K., additional, CHE, X.L., additional, JANG, Z., additional, FRAUENDORF, S., additional, DIMITROV, V., additional, ZHANG, JING-YE, additional, STEFANESCU, I., additional, GELBERG, A., additional, TER-AKOPIAN, G.M., additional, DANIEL, A.V., additional, STOYER, M.A., additional, DONANGELO, R., additional, COLE, J.D., additional, and STONE, N.J., additional

Published
2008
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36. EVIDENCE FOR CHIRAL DOUBLET BANDS IN 110,112Ru.

Author

LUO, Y. X., ZHU, S. J., HAMILTON, J. H., RASMUSSEN, J. O., RAMAYYA, A. V., GOODIN, C., LI, K., HWANG, J. K., CHE, X. L. ., JANG, Z., FRAUENDORF, S., DIMITROV, V., JING-YE ZHANG, STEFANESCU, I., GELBERG, A., TER-AKOPIAN, G. M., DANIEL, A. V., STOYER, M. A., DONANGELO, R., and COLE, J. D.

Subjects
RUTHENIUM isotopes, CHIRALITY of nuclear particles, NEUTRONS, NUCLEAR deformation, RADIOACTIVE decay
Published
2008

47. New band structures in Neutron-Rich Mo and Ru Isotopes

Author

Hamilton, J. H., Luo, Y. X., Zhu, S. J., Rasmussen, J. O., Ramayya, A. V., Goodin, C., Li, K., Jae-Kwang Hwang, Liu, S., Almehed, D., Frauendorf, S., Dimitrov, V., Zhang, Jing-Ye, Che, X. L., Jang, Z., Stefanescu, I., Gelberg, A., Ter-Akopian, G. M., Daniel, A. V., Lee, I. Y., Ding, H. -B, Xu, R. Q., Wang, J. -G, Xu, Q., Stoyer, M. A., Donangelo, R., and Stone, N. J.

Subjects
Physical Sciences, Nuclear & Particles Physics, Mathematical Sciences
Abstract

Rotational bands in 110,112Ru and 108Mo have been investigated by means of γ-γ-γ and γ-γ(θ) coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf. New δI = 1 negative parity doublet bands are found. These bands in 110,112Ru and 108Mo have all the properties expected for chiral vibrations. Microscopic calculations that combine the TAC meanfield with random phase approximation support this interpretation.

49. Anomalous spin dynamics in CdCu2(BO3)2 revealed by 11B NMR and ZF-μSR.

Author

Lee, W. -J., Do, S. -H., Sungwon Yoon, Jang, Z. H., Suh, B. J., Lee, J. H., Reyes, A. P., Kuhns, P. L., Luetkens, H., and Choi, K. -Y.

Subjects
*NUCLEAR magnetic resonance, *MUON spin rotation, *DIMERS, *MAGNETISM, *MAGNETIC transitions, *MAGNETIC anomalies
Abstract

We report 11B nuclear magnetic resonance (NMR) and zero-field muon spin relaxation (ZF-μSR) measurements of the anisotropic spin tetramer system CdCu2 (BO3)2, which consists of strongly interacting Cu(l) dimers and weakly coupled nonfrustrated Cu(2) spins. Long-range magnetic order is observed at TN = 9.8 K by a critical divergence of the nuclear spin-lattice relaxation rate 1/T1 and an appearance of well-defined muon-spin precessions. In addition, we find the spectroscopic signature for a magnetic anomaly at T* = 6.5 K, a few kelvins below TN. For temperatures below T*, 1/T1 ceases tofollow a T4.9(1) behavior. Instead, upon cooling below T*, both 1/T) and 1 /T2 become temperature-independent with a subsequent small drop. The muon frequency and the relative fraction of the Cu magnetic sites show anomalies mostly for Cu(2) spins at T*. This is ascribed to a Cu(2) spin reorientation. Site-specific change in magnetic structure is discussed in terms of the energy hierarchy of involved exchange interactions and an additional intertetramer interaction that controls magnetism at temperature T*. [ABSTRACT FROM AUTHOR]

Published
2014
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50. Evolution of chirality from γ soft 108Ru to triaxial 110,112Ru

Author

Luo, Y.X., Zhu, S.J., Hamilton, J.H., Rasmussen, J.O., Ramayya, A.V., Goodin, C., Li, K., Hwang, J.K., Almehed, D., Frauendorf, S., Dimitrov, V., Zhang, Jing-ye, Che, X.L., Jang, Z., Stefanescu, I., Gelberg, A., Ter-Akopian, G.M., Daniel, A.V., Stoyer, M.A., and Donangelo, R.

Subjects
*CHIRALITY of nuclear particles, *NUCLEAR fission, *RUTHENIUM, *APPROXIMATION theory, *MICROSCOPY, *RANDOM fields
Abstract

Abstract: Rotational bands in 108,110,112Ru have been investigated by means of and coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf. The positive parity bands are described by different versions of IBA, where 108Ru is best described as a γ-soft nucleus whereas 110,112Ru are more like rigid triaxial rotors. New negative parity doublet bands are found. In case of 110,112Ru, these are interpreted as soft chiral vibrations. Many of the experimental findings can be explained by microscopic calculations that combine the TAC mean-field with random phase approximation but a simple geometrical explanation is not apparent. [Copyright &y& Elsevier]

Published
2009
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