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Start Over Author "Zhang, Q." Journal applied physics letters
458 results on '"Zhang, Q."'

2. Magnetic fingerprint of interfacial coupling between CoFe and nanoscale ferroelectric domain walls

Author

Zhang, Q, Murray, P, You, L, Wan, C, Zhang, X, Li, W, Khan, U, Wang, J, Liu, K, and Han, X

Subjects
cond-mat.mtrl-sci, cond-mat.mes-hall, Applied Physics, Engineering, Physical Sciences, Technology
Abstract

Magnetoelectric coupling in ferromagnetic/multiferroic systems is often manifested in the exchange bias effect, which may have combined contributions from multiple sources, such as domain walls, chemical defects, or strain. In this study we magnetically "fingerprint" the coupling behavior of CoFe grown on epitaxial BiFeO3 (BFO) thin films by magnetometry and the first-order-reversal-curves (FORC). The contribution to exchange bias from 71°, 109° and charged ferroelectric domain walls (DWs) was elucidated by the FORC distribution. CoFe samples grown on BFO with 71° DWs only exhibit an enhancement of the coercivity, but little exchange bias. Samples grown on BFO with 109° DWs and mosaic DWs exhibit a much larger exchange bias, with the main enhancement attributed to 109° and charged DWs. Based on the Malozemoff random field model, a varying-anisotropy model is proposed to account for the exchange bias enhancement. This work sheds light on the relationship between the exchange bias effect of the CoFe/BFO heterointerface and the ferroelectric DWs, and provides a path for multiferroic device analysis and design.

Published
2016

7. A facile strategy to produce monatomic tantalum metallic glass

Author

Zhao, R., primary, Jiang, H. Y., additional, Luo, P., additional, Sun, Y. T., additional, Li, Z. A., additional, Wu, W. W., additional, Shen, L. Q., additional, Liu, M., additional, Zhao, S. F., additional, Wen, P., additional, Zhang, Q. H., additional, Gu, L., additional, Bai, H. Y., additional, and Wang, W. H., additional

Published
2020
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12. Dielectric enhancement over a broad temperature by nanofiller at ultra-low volume content in poly(ether methyl ether urea).

Author

Tian Zhang, Xin Chen, Qiyan Zhang, and Zhang, Q. M.

Subjects
DIELECTRICS, PERMITTIVITY, UREA, DIELECTRIC loss, NANOCOMPOSITE materials, METHYL ether
Abstract

This Letter studies the dielectric responses of nanocomposites of poly(ether methyl ether urea) (PEMEU) with alumina nanofillers at less than 0.7% volume loading (0.7 vol. %). The results show that the dielectric constant K of PEMEU nanocomposites is enhanced by the nanofillers. The enhancement peaks at 0.33 vol. % nanofiller loading, from K = 3.9 of neat polymer to K = 5.5 of nanocomposites from room temperature to 200 °C, above the glass transition (∼150 °C) of the polymer. Except for an enhanced dielectric constant, the nanocomposite maintains a low dielectric loss and a high breakdown strength of 500 MV/m at room temperature and 300 MV/m at 150 °C, respectively. Thus, the nanocomposite with 0.33 vol. % nanofillers delivers discharged energy densities of 6.5 J/cm³ at room temperature and 2 J/cm³ at 150 °C with better than 90% charge/discharge efficiency, 40% higher than the neat polymer. [ABSTRACT FROM AUTHOR]

Published
2020
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23. Perovskite LaBaCo2O5+δ (LBCO) single-crystal thin films for pressure sensing applications.

Author

Ma, Y. J., Xiao, J. Y., Zhang, Q. Y., Ma, C. Y., Jiang, X. N., Wu, B. Y., and Zeng, X. Y.

Subjects
ELECTRIC properties, PEROVSKITE, MAGNETRON sputtering, POLYCRYSTALS, PRESSURE sensors, THIN films
Abstract

Perovskite LaBaCo2O5+δ (LBCO) single-crystal films were deposited on (001) MgO substrates by a magnetron sputtering method and processed into Pirani sensors for investigation of pressure measurements. In comparison to the poly-crystal film deposited under the same condition, the single-crystal LBCO films exhibited rather a large temperature coefficient of resistance and a high sensitivity in response to pressure. The LBCO sensors with dimensions of 30 to 200 μm, which are different from resistor-on-dielectric membrane or micro-beam structures, demonstrated to be capable of making response to the pressures ranging from 5 × 10–2 to 105 Pa with a real dynamic range of 3 to 2 × 103 Pa. [ABSTRACT FROM AUTHOR]

Published
2018
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29. Perpendicular magnetic anisotropy in Ta|Co40Fe40B20|MgAl2O4 structures and perpendicular CoFeB|MgAl2O4|CoFeB magnetic tunnel junction

Author

Tao, B. S., primary, Li, D. L., additional, Yuan, Z. H., additional, Liu, H. F., additional, Ali, S. S., additional, Feng, J. F., additional, Wei, H. X., additional, Han, X. F., additional, Liu, Y., additional, Zhao, Y. G., additional, Zhang, Q., additional, Guo, Z. B., additional, and Zhang, X. X., additional

Published
2014
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30. An electrocaloric refrigerator with direct solid to solid regeneration.

Author

Tian Zhang, Xiao-Shi Qian, Haiming Gu, Ying Hou, and Zhang, Q. M.

Subjects
REGENERATIVE cooling, REFRIGERATORS, ELECTRIC fields, PYROELECTRICITY, COOLING
Abstract

Regenerative cooling has been used to improve the efficiency of refrigerators. Recently, exploiting the easy controlling of the electric fields, a regenerative electrocaloric (EC) cooling device with direct solid to solid regeneration has been proposed. Here, we report an experimental study of such an EC cooling device. For the EC device to be operated at a household voltage, the EC multilayer ceramic elements were first developed employing the multilayer ceramic capacitor fabrication technique. Under a voltage of 200 V, the EC multilayers with the commercial Y5V ceramic composition exhibit an electric field induced temperature change DT of 0.86 K. Testing results of a prototype EC device based on these EC multilayer elements show that even with only two EC rings, which is the minimum unit required to demonstrate the operation, such an EC device can generate a temperature span between hot and cold ends about three times of DT of the EC multilayers. [ABSTRACT FROM AUTHOR]

Published
2017
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31. Exchange coupled Mn-Mn pair: An approach for super-broadband 1380nm emission in α-MnS.

Author

Chen, Z. T., Song, E. H., Wu, M., Zhou, B., and Zhang, Q. Y.

Subjects
BROADBAND communication systems, NEAR infrared radiation, MANGANOUS sulfide, PHOTOLUMINESCENCE, EXCHANGE interactions (Magnetism)
Abstract

Super-broadband near-infrared (NIR) emission centered at 1380 nm with a full width at half maximum of 161nm and a decay lifetime of 241 μs has been demonstrated in a-MnS. We find that the NIR emission originates from exchange coupled Mn-Mn pairs in a-MnS based on the detail analysis of photoluminescence excitation spectra, transient spectra, temperature dependent photoluminescence spectra as well as the crystal structure of a-MnS. Mechanism of exchange interaction between nearest-neighbor Mn2+ ions is discussed in detail. The finding offers the possibilities of designing NIR emitting source for various photonic applications. [ABSTRACT FROM AUTHOR]

Published
2016
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44. Anomalous negative electrocaloric effect in a relaxor/normal ferroelectric polymer blend with controlled nano- and meso-dipolar couplings.

Author

Xiaoshi Qian, Tiannan Yang, Tian Zhang, Long-Qing Chen, and Zhang, Q. M.

Subjects
PYROELECTRICITY, RELAXOR ferroelectrics, DIELECTRIC materials, FERROELECTRIC polymers, COORDINATE covalent bond, HEAT radiation & absorption
Abstract

In general, a dielectric material will eject (or absorb) heat when an electric field is applied and absorb (or eject) heat when the field is removed, under isothermal condition, which is known as the normal (or negative) electrocaloric (EC) effect. For some applications, it is highly desired that an EC material will absorb heat (cooling the surrounding) without subsequent heating under an electric pulse. Here, we show that such an EC material can be realized in a properly designed hybrid normal ferroelectric/relaxor ferroelectric polymer blend in which the normal ferroelectric component induces dipole ordering in the relaxor polymer in the poled state, which can be switched to a de-poled state by an external field. More importantly, the de-poled state can be maintained by the relaxor component when the de-poling field is removed. Consequently, the hybrid blend exhibits a large cooling (an isothermal entropy change ΔS=11.5 J kg–1K–1) without the subsequent heating upon the application of an electric pulse. [ABSTRACT FROM AUTHOR]

Published
2016
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45. Enhanced electrocaloric effect in composition gradient bilayer thick films.

Author

Ying Hou, Lu Yang, Xiaoshi Qian, Tian Zhang, and Zhang, Q. M.

Subjects
PYROELECTRICITY, CONJUGATE gradient methods, THICK films, ELECTRIC fields, SURFACE coatings
Abstract

We report the enhanced electrocaloric (EC) response over a broad temperature range in composition gradient Ba(ZrTi)O3 based bilayer thick films. A large EC temperature change of -4.9K under an electric field of 10MV/m around room temperature, large electrocaloric coefficient ΔT/ΔE = 0.49 × 10-6K m V-1 were observed in the BaZr0.17Ti0.83O3/BaZr0.20Ti0.80O3 bilayer thick films, which are improved compared with BaZr0.20Ti0.80O3 and BaZr0.17Ti0.83O3 homogeneous bilayer films. The result reveals the potential of the composition gradient bilayer structure in improving the electrocaloric effect, which may provide an effective route to achieve large EC temperature change under a low electric field. [ABSTRACT FROM AUTHOR]

Published
2016
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