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20. Anomalous magnetic configuration of Mn2NiAl ribbon and the role of hybridization in the martensitic transformation of Mn50Ni50-xAlx ribbons.

Author

Zhao, R. B., Zhao, D. W., Li, G. K., Ma, L., Zhen, C. M., Hou, D. L., Wang, W. H., Liu, E. K., Chen, J. L., and Wu, G. H.

Subjects
NICKEL-manganese alloys, MARTENSITIC transformations, LATTICE constants, ANTIFERROMAGNETIC materials, FERROMAGNETISM, EXCHANGE interactions (Magnetism)
Abstract

The magnetic configuration of Mn2NiAl ribbon has been investigated. In contrast to Ni2MnAl, the compound Mn2NiAl with considerable disorder does exhibit ferromagnetism and, due to exchange interaction competition, both ferromagnetic and antiferromagnetic moment orientations can coexist between nearest neighbor Mn atoms. This is unexpected in Heusler alloys. Regarding the mechanism of the martensitic transformation in Mn50Ni50_xAlx, it is found that increasing the Al content results in an unusual change in the lattice constant, a decrease of the transformation entropy change, and enhancement of the calculated electron localization. These results indicate that the p-d covalent hybridization between Mn (or Ni) and Al atoms gradually increases at the expense of the d-d hybridization between Ni and Mn atoms. This leads to an increased stability of the austenite phase and a decrease of the martensitic transformation temperature. For 11 ≤ x ≤ 14, Mn50Ni50_xAlx ferromagnetic shape memory alloys are obtained. [ABSTRACT FROM AUTHOR]

Published
2014
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24. Schottky behavior at InN–GaN interface

Author

Chen, N. C., primary, Chang, P. H., additional, Wang, Y. N., additional, Peng, H. C., additional, Lien, W. C., additional, Shih, C. F., additional, Chang, Chin-An, additional, and Wu, G. M., additional

Published
2005
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25. Superelasticity of CoNiGa:Fe single crystals

Author

Dai, X. F., primary, Liu, G. D., additional, Liu, Z. H., additional, Wu, G. H., additional, Chen, J. L., additional, Meng, F. B., additional, Liu, H. Y., additional, Yan, L. Q., additional, Qu, J. P., additional, Li, Y. X., additional, Wang, W. G., additional, and Xiao, John Q., additional

Published
2005
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40. Magneto-transport properties of oriented Mn2CoAl films sputtered on thermally oxidized Si substrates.

Author

Xu, G. Z., Du, Y., Zhang, X. M., Zhang, H. G., Liu, E. K., Wang, W. H., and Wu, G. H.

Subjects
MAGNETIC properties of Heusler alloys, NARROW gap semiconductors, SILICON surfaces, MAGNETRON sputtering, ANOMALOUS Hall effect, MAGNETORESISTANCE measurement, X-ray photoelectron spectroscopy, ENERGY dispersive X-ray spectroscopy
Abstract

The article discusses a research related to the investigation of fabrication and transport properties of spin gapless Heusler alloy Mn2CoAl films prepared on thermally oxidised silicon (Si) substrates by deposition using magnetron sputtering. Topics discussed include films deposition at 673 Kelvin, analysis of resistivity, anomalous Hall conductivity and linear magnetoresistance and use of energy-dispersive X-ray and X-ray photoelectron spectroscopy for elements characterization.

Published
2014
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43. Unusual magnetic anisotropy in the ferromagnetic shape-memory alloy Ni50Fe23Ga27.

Author

Qian, J. F., Liu, E. K., Feng, L., Zhu, W., Li, G. J., Wang, W. H., Wu, G. H., Du, Z. W., and Fu, X.

Subjects
ANISOTROPY, IRON-nickel alloys, GALLIUM alloys, FERROMAGNETIC materials, SHAPE memory alloys, AUSTENITE, MARTENSITE
Abstract

Unusual magnetic anisotropy of the ferromagnetic shape-memory alloy Ni50Fe23Ga27 has been observed. The anisotropy of the austenite becomes very large, even larger than that of the martensite in ribbon samples. Lowering the temperature from 300 K to 80 K, the saturation field of the austenite is dramatically increased from 200 Oe up to 6 kOe. This high-anisotropy behavior clearly highlights the demagnetization effect of the martensitic transformation. The physical mechanism is attributed to a collective effect coming from the atomic disorder, the premartensitic transformation, and the off-stoichiometric Ga-rich composition of the alloys. [ABSTRACT FROM AUTHOR]

Published
2011
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44. Giant exchange bias based on magnetic transition in γ-Fe2MnGa melt-spun ribbons.

Author

Tang, X. D., Wang, W. H., Zhu, W., Liu, E. K., Wu, G. H., Meng, F. B., Liu, H. Y., and Luo, H. Z.

Subjects
EXCHANGE reactions, PHASE transitions, IRON compounds, MELT spinning, ANTIFERROMAGNETISM, ANISOTROPY, MAGNETIC fields
Abstract

Giant exchange bias with a shift up to 3.86 kOe has been observed in γ-Fe2MnGa alloy in which a ferromagnetic to antiferromagnetic transition takes place at 250 K. The transition can be suppressed to lower temperatures by higher magnetic fields at a shift rate of 10.3 K/kOe. Exchange bias and enhanced coercivity occur simultaneously, revealing an exchange coupling between the coexisting antiferromagnetic and ferromagnetic phases. Meanwhile, the internal exchange coupling inside the antiferromagnetic clusters dynamically ensures their unidirectional anisotropy during their size changing following the external magnetic field. [ABSTRACT FROM AUTHOR]

Published
2010
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45. Intrinsic electron doping in nominal “nondoped” superconducting (La,Y)2CuO4 thin films grown by magnetron sputtering.

Author

Zhao, L., Wu, G., Liu, R. H., and Chen, X. H.

Subjects
*SUPERCONDUCTORS, *THIN films, *MAGNETRONS, *SPUTTERING (Physics), *LANTHANUM, *YTTRIUM
Abstract

The superconducting nominal “nondoped” La1.85Y0.15CuO4 (LYCO) thin films are prepared by magnetron sputtering. The best TC0 of more than 13 K is achieved in the optimal films with highly pure c-axis oriented T′-type structure. The quasiquadratic temperature dependence of resistivity and the negative Hall coefficient in the normal state, effect of oxygen content are all quite similar to the known Ce-doped n-type cuprate superconductors, suggesting the electron-doping nature in T′-LYCO. The charge carriers are considered to arise from oxygen deficiency. [ABSTRACT FROM AUTHOR]

Published
2007
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46. Large magnetoresistance in single-crystalline Ni50Mn50-xInx alloys (x=14–16) upon martensitic transformation.

Author

Yu, S. Y., Liu, Z. H., Liu, G. D., Chen, J. L., Cao, Z. X., Wu, G. H., Zhang, B., and Zhang, X. X.

Subjects
CRYSTALS, MAGNETORESISTANCE, ELECTRONIC structure, ELECTRIC fields, ELECTRIC resistance, MARTENSITIC transformations
Abstract

Variation of electrical resistance in single-crystalline Ni50Mn50-xInx alloys (x=14–16) upon martensitic transformation was investigated. In Ni50Mn35In15 with Tm∼295 K, a negative magnetoresistance (MR) over 60% is attainable at moderate field strengths; in Ni50Mn34In16 with Tm∼190 K, the MR can exceed 70% over a temperature of approximately 100 K. The significant change in electric resistance upon martensitic transformation originates primarily from the altered electronic structure, while the large effect of a magnetic field follows its ability to manipulate the transformation in materials of low Tm and large ΔM/ΔS. The extremely large MR promises more innovative applications for these important alloys. [ABSTRACT FROM AUTHOR]

Published
2006
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47. Magnetically controlled high damping in ferromagnetic Ni52Mn24Ga24 single crystal.

Author

Wang, W. H., Liu, G. D., and Wu, G. H.

Subjects
FERROMAGNETIC materials, MARTENSITIC transformations, DAMPING (Mechanics), MAGNETIC domain, INTERNAL friction, SHAPE memory alloys, CRYSTALS at low temperatures
Abstract

An unusually high damping peak of 20% has been observed in Ni52Mn24Ga24 single crystals accompanying with martensitic transformation. The high damping capacity can be retained in the low-temperature martensite phase when a bias field of 0.4 T was applied along the measurement direction. The magnetically controlled high damping and adjustable martensitic-austenitic transformation temperature indicate a great potential of using Ni–Mn–Ga alloys as high damping or energy absorbing materials in a wide temperature range. [ABSTRACT FROM AUTHOR]

Published
2006
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48. Martensitic transformation and shape memory effect in a ferromagnetic shape memory alloy: Mn2NiGa.

Author

Liu, G. D., Chen, J. L., Liu, Z. H., Dai, X. F., Wu, G. H., Zhang, B., and Zhang, X. X.

Subjects
MARTENSITIC transformations, MARTENSITE, SHAPE memory alloys, ALLOYS, METALLIC composites, FERROMAGNETIC materials, MAGNETIC fields
Abstract

Heusler alloy Mn2NiGa has been developed by synthesizing a series of ferromagnetic shape memory alloys Mn25+xNi50-xGa25 (x=0–25). Mn2NiGa exhibits a martensitic transformation around room temperature with a large thermal hysteresis up to 50 K and a lattice distortion as large as 21.3% and has a quite high Curie temperature of 588 K. The martensite shows a high-saturated field up to 2 T. The excellent two-way shape memory behavior with a strain of 1.7% was observed in the single crystal Mn2NiGa. The magnetic-field-controlled effect created a total strain up to 4.0% and changed the sign of the shape deformation effectively. [ABSTRACT FROM AUTHOR]

Published
2005
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49. Large negative magnetoresistance in quaternary Heusler alloy Ni50Mn8Fe17Ga25 melt-spun ribbons.

Author

Liu, Z. H., Liu, H., Zhang, X. X., Zhang, X. K., Xiao, John Q., Zhu, Z. Y., Dai, X. F., Liu, G. D., Chen, J. L., and Wu, G. H.

Subjects
MAGNETORESISTANCE, CHROMIUM-cobalt-nickel-molybdenum alloys, ELECTRONS, FERROMAGNETISM, MAGNETIC fields, ANISOTROPY
Abstract

Quaternary Heusler alloy Ni50Mn8Fe17Ga25 ribbons have been prepared by the melt-spun method. The ribbons exhibit large negative magnetoresistance (MR){=[R(H)-R(0)]/R(0)} over a wide temperature region, particularly in the region during the martensitic phase transformation. The MR decreases significantly after annealing. The large MR is isotropic and is mainly attributed to the local magnetic disorders, magnetic clusters, and heterogeneity. The maximum MR at martensitic transformation may be due to the redistribution of electrons and the increase of phase boundary scattering. This feature adds a useful functionality to the already interesting Heusler alloys. [ABSTRACT FROM AUTHOR]

Published
2005
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50. Large magnetostriction in Fe100-xAlx (15≤x≤30) melt-spun ribbons.

Author

Liu, Z. H., Liu, G. D., Zhang, M., Wu, G. H., Meng, F. B., Liu, H. Y., Yan, L. Q., Qu, J. P., and Li, Y. X.

Subjects
MAGNETOSTRICTION, MAGNETISM, ALLOYS, METALLIC composites, PHASE equilibrium, COMPOSITE materials
Abstract

Magnetostriction of Fe100-xAlx (15≤x≤30) al1oys has been largely improved by using melt-spun method. The large magnetostriction up to -700 ppm obtained in Fe81Al19 sample is about 5 times as large as that in conventional bulk samples of Fe–Al composition. It has been ascribed to the high concentration of Al–Al atom pairs created by melting-spinning method and their strongly preferential orientation in [100] textured ribbon plane. The remarkable anisotropic magnetostriction reflects the magnetoelastic competition occurring in those strong textured and thin ribbon samples. The composition dependence of the magnetostriction in ribbon samples has been found to be consistent with bulk materials. [ABSTRACT FROM AUTHOR]

Published
2004
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