Y.W. Du

Publications (65)140.21 Total impact

• Article: Giant positive magnetoresistance in heterostructure (La0.7Sr0.3MnO3) coated with YBa2Cu3O7 composites

  Y. B. Lin, Z. G. Huang, Y. M. Yang, S. Wang, S. D. Li, F. M. Zhang, Y. W. Du
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  ABSTRACT: (La0.7Sr0.3MnO3) x /(YBa2Cu3O7) y composites were prepared by mixing La0.7Sr0.3MnO3 powders and the sol–gel-derived YBa2Cu3O7 matrix, followed by high-temperature calcinations. Their structural, magnetic properties and magnetoresistance effect have been investigated systematically. A giant positive magnetoresistance (PMR) at low magnetic field is observed at low temperatures. In the case of (La0.7Sr0.3MnO3)1/(YBa2Cu3O7)9 composite, the PMR achieves 260% under a magnetic field of 5800Oe. However, the PMR value sharply decreases with increasing temperature and no magnetoresistance effects are found above metal-insulator transition temperature. The enhancement of spin-dependent scattering at the grain boundaries should be responsible for the observed PMR. In addition, the temperature dependence of resistance under magnetic field could be explained by the competition between diamagnetism and paramagnetism in YBCO phase. At low temperature, the diamagnetism is predominant over paramagnetism and the interface scattering between LSMO grains is enhanced correspondingly. As a result, the low-temperature resistance increases and large PMR appears.
  Applied Physics A 04/2012; 104(1):143-147. · 1.63 Impact Factor
• Article: Study of uniaxial magnetism and enhanced magnetostriction in magnetic-annealed polycrystalline CoFe2O4

  Y. X. Zheng, Q. Q. Cao, C. L. Zhang, H. C. Xuan, L. Y. Wang, D. H. Wang, Y. W. Du
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  ABSTRACT: Magnetic and magnetostrictive properties of magnetic-annealed polycrystalline CoFe2O4 were investigated. The magnetic hysteresis loops showed obvious uniaxiality with an induced easy direction parallel to the annealing field. Magnetic force microscopy study revealed that the domains were fixed by magnetic annealing. The uniaxial behavior was also observed in the magnetostrictive measurement, which showed a significantly enhanced magnetostriction of − 273 PPM when the external field was applied perpendicular to the annealing field direction. A physical mechanism for the effect of magnetic annealing on polycrystalline CoFe2O4 is developed, in which the induced uniaxiality is ascribed to the realignment of easy axes in polycrystals. The uniaxial behavior of magnetism and enhanced magnetostriction could be well explained by this model.
  Journal of Applied Physics 08/2011; 110(4):043908-043908-7. · 2.17 Impact Factor
• Article: Electric field control of magnetism without magnetic bias field in the Ni/Pb(Mg1/3Nb2/3)O3-PbTiO3/Ni composite

  H. C. Xuan, L. Y. Wang, Y. X. Zheng, Y. L. Li, Q. Q. Cao, S. Y. Chen, D. H. Wang, Z. G. Huang, Y. W. Du
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  ABSTRACT: This paper reports on the electric field control of magnetism without magnetic bias field in a Ni/Pb(Mg1/3Nb2/3)O3-PbTiO3/Ni composite prepared by electrochemical deposition. The converse magnetoelectric effect, which was measured by an induction method, shows a peak value of 0.45 G/V at the resonance frequency of 102 kHz. Without magnetic bias field, the magnetization of the Ni layers can be controlled by an applied dc electric field in a reversible and reproducible way and shows an analogous on-off behavior with the electric field switching on and off alternatively.
  Applied Physics Letters 07/2011; 99(3):032509-032509-3. · 3.84 Impact Factor
• Article: Large and highly reversible magnetic field-induced strains in textured Co1−xNixMnSi alloys at room temperature

  C L Zhang, Y X Zheng, H C Xuan, S C Ma, Q Q Cao, D H Wang, Y W Du
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  ABSTRACT: The metamagnetic transition and magnetoelastic properties are investigated in transition-metal-based Co1−xNixMnSi (0 < x < 0.03) alloys. Large low-field magnetostrains are observed in the Ni-doped CoMnSi alloys. Compared with some other metamagnetic materials with large magnetic field-induced strains, the present alloys show highly reversible magnetoelastic behaviour and have almost constant strain outputs around room temperature. These observations may shed light on developing transition-metal-based magnetostrictive materials.
  Journal of Physics D Applied Physics 03/2011; 44(13):135003. · 2.54 Impact Factor
• Article: The martensitic transformation, magnetocaloric effect, and magnetoresistance in high-Mn content Mn47+xNi43−xSn10 ferromagnetic shape memory alloys

  H. C. Xuan, Y. X. Zheng, S. C. Ma, Q. Q. Cao, D. H. Wang, Y. W. Du
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  ABSTRACT: A series of high-Mn content Mn47+xNi43−xSn10 (x = 0, 1, 2, 3, 4, and 5) ferromagnetic shape memory alloys were prepared by arc melting method. The martensitic transformation were observed in these alloys, even the content of Mn is higher than 50 at. %. The phase transition temperature of these alloys can be adjusted by tuning the compositions of Ni and Mn. Large positive magnetic entropy change and negative magnetoresistance which originate from the magnetic-field-induced martensitic transformation are obtained in these alloys.
  Journal of Applied Physics 11/2010; 108(10):103920-103920-4. · 2.17 Impact Factor
• Source

  Available from: 144.206.159.178

  Article: Investigation of the intermediate phase and magnetocaloric properties in high-pressure annealing Ni–Mn–Co–Sn alloy

  S. C. Ma, H. C. Xuan, C. L. Zhang, L. Y. Wang, Q. Q. Cao, D. H. Wang, Y. W. Du
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  ABSTRACT: The Ni–Mn–Co–Sn alloy is prepared by high-pressure annealing method. Besides the enhanced martensitic transformation temperature and the Curie temperature of austenite, an intermediate phase above the martensitic transformation is observed in this alloy. As a result, two successive magnetic entropy changes with the same sign are obtained around room-temperature, corresponding to the martensitic transformation and intermediate phase transition, respectively. The origin of the intermediate phase for high-pressure annealing Ni–Mn–Co–Sn alloy is discussed.
  Applied Physics Letters 08/2010; 97(5):052506-052506-3. · 3.84 Impact Factor
• Article: Large exchange bias field in the Ni–Mn–Sn Heusler alloys with high content of Mn

  H. C. Xuan, Q. Q. Cao, C. L. Zhang, S. C. Ma, S. Y. Chen, D. H. Wang, Y. W. Du
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  ABSTRACT: The exchange bias properties have been investigated in bulk Mn ₅₀ Ni _{40- x} Sn _{10+ x} ( x =0 , 0.5, and 1) Heusler alloys with high content of Mn, in which the largest exchange bias field is up to 910 Oe for Mn ₅₀ Ni ₄₀ Sn ₁₀ alloy. In these alloys, the excess Mn atoms would occupy not only the Sn sites but also the Ni sites, and the moments of Mn on Sn or Ni sites are coupled antiferromagnetically to those on the regular Mn sites, respectively. The origin of this considerably large exchange bias field has been discussed.
  Applied Physics Letters 06/2010; · 3.84 Impact Factor
• Source

  Available from: cmp.fjnu.edu.cn

  Article: Converse magnetoelectric effect in ferromagnetic shape memory alloy/piezoelectric laminate

  S. Y. Chen, D. H. Wang, Z. D. Han, C. L. Zhang, Y. W. Du, Z. G. Huang
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  ABSTRACT: In laminates, the converse magnetoelectric (CME) effect is often achieved by an elastic coupling between magnetostrictive and piezoelectric layers. Here the authors report on an alternative mechanism for obtaining CME. In a transition-metals-based ferromagnetic shape memory alloy/piezoelectric ceramic laminated composite, the stress-induced martensitic transformation is utilized to gain the magnetic changes, which gives rise to a giant CME effect consequently. The strong CME is observed at room temperature over a broad bandwidth, under weak magnetic bias and electric field.
  Applied Physics Letters 07/2009; 95(2):022501-022501-3. · 3.84 Impact Factor
• Article: Large magnetic entropy changes in Gd–Co amorphous ribbons

  C. L. Zhang, D. H. Wang, Z. D. Han, H. C. Xuan, B. X. Gu, Y. W. Du
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  ABSTRACT: A series of magnetic amorphous ribbons with different Gd/Co ratios was prepared by melt-spun method. With the decrease in Gd/Co ratio, Curie temperatures increase gradually from 166 to 193 K. The maximum values of magnetic entropy changes under a magnetic field of 10 kOe are -3.1 , -3.0 , -2.9 , and -2.8 J / kg   K for Gd ₇₁ Co ₂₉ , Gd ₆₈ Co ₃₂ , Gd ₆₅ Co ₃₅ , and Gd ₆₂ Co ₃₈ samples, respectively. The approximately constant peak values of ΔS_M at different working temperatures indicate that they are advantageous for an Ericsson refrigeration cycle. In addition, these samples have large resistivity and greatly reduced magnetic hysteresis losses, which could increase the refrigeration efficiency. These advantages make the Gd–Co amorphous ribbons good candidates for the practical magnetic refrigeration.
  Journal of Applied Physics 02/2009; · 2.17 Impact Factor
• Article: Large magnetic entropy change and broad working temperature span in CoMnSi0.88Ge0.12 alloy

  C L Zhang, D H Wang, Q Q Cao, Z D Han, H C Xuan, Y W Du
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  ABSTRACT: CoMnSi0.88Ge0.12 alloy was prepared using an optimized annealing routine. The metamagnetic transition between antiferromagnetism and ferromagnetism can be observed in this alloy by either increasing the temperature or applying a magnetic field. The metamagnetic transition temperature is very sensitive to the applied field. Owing to the low metamagnetic critical field and large variation in magnetization, large and positive magnetic entropy changes as well as broad working temperature spans are obtained in this metamagnetic system.
  Journal of Physics D Applied Physics 12/2008; 42(1):015007. · 2.54 Impact Factor
• Article: Effect of annealing on the martensitic transformation and magnetoresistance in Ni–Mn–Sn ribbons

  H C Xuan, Y Deng, D H Wang, C L Zhang, Z D Han, Y W Du
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  ABSTRACT: Ni44.1Mn44.2Sn11.7 ribbons were prepared by melt spinning. After heat treatment, the martensitic transformation (MT) temperature increases obviously in the annealed ribbons. Large magnetoresistance (MR) was observed in these ribbons. Under the field of 50 kOe, the maximum values of negative MR were 22% for melt-spun ribbons at 240 K and 38% for annealed ribbons at 268 K, respectively. The annealing effect on MT and MR, together with the origin of the large MR, has been discussed in this paper.
  Journal of Physics D Applied Physics 10/2008; 41(21):215002. · 2.54 Impact Factor
• Article: The phase transitions, magnetocaloric effect, and magnetoresistance in Co doped Ni–Mn–Sb ferromagnetic shape memory alloys

  Z. D. Han, D. H. Wang, C. L. Zhang, H. C. Xuan, J. R. Zhang, B. X. Gu, Y. W. Du
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  ABSTRACT: The phase transitions, magnetocaloric effect, and magnetoresistance in Ni _50-x Co _x Mn ₃₉ Sb ₁₁ (x=0–11) ferromagnetic shape memory alloys were investigated. The temperatures of martensitic transformation and magnetic transition in austenitic phase depend strongly on the Co concentration, while the magnetic transition temperature in martensitic phase shows small dependence on alloy composition. For 7≤x≤9 , the martensitic transformation is accompanied by a sudden change in magnetization. Large positive magnetic entropy changes and negative magnetoresistance near room temperature, which originate from the magnetic-field-induced transformation from the weak-magnetic high-resistance martensitic phase to the ferromagnetic low-resistance parent phase, are observed in these alloys. Our results indicate the potential application of Ni _50-x Co _x Mn ₃₉ Sb ₁₁ alloys in magnetic refrigeration and magnetic sensors.
  Journal of Applied Physics 10/2008; · 2.17 Impact Factor
• Article: Magnetostructural phase transition and magnetocaloric effect in off-stoichiometric Mn1.9−xNixGe alloys

  C. L. Zhang, D. H. Wang, Q. Q. Cao, Z. D. Han, H. C. Xuan, Y. W. Du
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  ABSTRACT: Phase transitions and magnetic entropy changes are studied in Mn1.9−xNixGe (x = 0.85, 0.855) alloys. In these off-stoichiometric alloys, the crystallographic transition temperature decreases remarkably due to the deficiency of transition-metal atoms, and, consequently, a magnetostructural transition from the antiferromagnetic TiNiSi-type structure to the ferromagnetic Ni2In-type structure is observed. Owing to the abrupt change in magnetization, large magnetic entropy changes are obtained. The effect of transition-metal vacancies on the phase transition temperature is discussed.
  Applied Physics Letters 09/2008; 93(12):122505-122505-3. · 3.84 Impact Factor
• Source

  Available from: fjnu.edu.cn

  Article: Ferromagnetism of Co-doped TiO2 films prepared by plasma enhanced chemical vapour deposition (PECVD) method

  Y B Lin, Y M Yang, B Zhuang, S L Huang, L P Wu, Z G Huang, F M Zhang, Y W Du
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  ABSTRACT: Ti1−xCoxO2 polycrystalline films have been prepared on Si(0 0 1) substrates by the plasma enhanced chemical vapour deposition technique at 280 °C without using any carrier gas. All the films show room-temperature ferromagnetic behaviours and no ferromagnetic clusters are detected by x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, Raman and superconducting quantum interference device measurements as the doping concentration is lower than 4%. In addition, the formation of non-ferromagnetic CoTiO3 under heavy doping is considered to be responsible for the degradation of magnetization in Ti1−xCoxO2 polycrystalline films. Furthermore, saturated magnetization of Ti1−xCoxO2 films is found to decrease with the increasing duration of oxygen-plasma processing, indicating that the oxygen vacancies in the films play an important role in the generation of ferromagnetic Ti1−xCoxO2 films.
  Journal of Physics D Applied Physics 09/2008; 41(19):195007. · 2.54 Impact Factor
• Article: Influence of the oxidative annealing temperature on the magnetism of (Mn, N)-codoped ZnO thin films

  Z. L. Lu, G. Q. Yan, S. Wang, W. Q. Zou, Z. R. Mo, L. Y. Lv, F. M. Zhang, Y. W. Du, M. X. Xu, Z. H. Xia
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  ABSTRACT: (Mn, N)-codoped ZnO films have been achieved by oxidative annealing of sputtered Zn ₂ N ₃: Mn films at different temperatures in flowing O ₂ ambient. X-ray diffraction measurements and x-ray photoelectron spectroscopy studies indicate that both divalent Mn ²⁺ and trivalent N ^3- ions are incorporated into ZnO lattice. Ferromagnetism with Curie temperature above 300 K was observed in the (Mn, N)-codoped ZnO films and found to be sensitive to the oxidative annealing temperature due to its strong effect on the carrier type and concentration. The strongest ferromagnetism has been found in the (Mn, N)-codoped ZnO films with the highest hole concentration in this study. The results indicate that holes are favorable for ferromagnetic ordering of doped Mn ²⁺ ions in ZnO in agreement with the recent theoretical studies. The mechanism of ferromagnetic coupling in (Mn, N)-codoped ZnO is discussed.
  Journal of Applied Physics 09/2008; · 2.17 Impact Factor
• Article: Effect of annealing on the martensitic transformation and magnetocaloric effect in Ni44.1Mn44.2Sn11.7 ribbons

  H. C. Xuan, K. X. Xie, D. H. Wang, Z. D. Han, C. L. Zhang, B. X. Gu, Y. W. Du
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  ABSTRACT: The Ni44.1Mn44.2Sn11.7 ribbons were prepared by melt spinning. A single-phase austenite with L21 structure was confirmed in the melt-spun ribbons at room temperature. After the heat treatment, the martensitic transformation temperature increases obviously in the annealed ribbons. This method may be an effective way to tune the characteristic temperatures in the ferromagnetic shape memory alloys. Giant magnetic entropy changes are observed in the annealed ribbons. The peak values at 10 kOe are 32.1 and 20.1 J/kg K, for the ribbons annealed at 1123 and 1173 K, respectively.
  Applied Physics Letters 06/2008; 92(24):242506-242506-3. · 3.84 Impact Factor
• Article: Boron’s effect on martensitic transformation and magnetocaloric effect in Ni43Mn46Sn11Bx alloys

  H. C. Xuan, D. H. Wang, C. L. Zhang, Z. D. Han, B. X. Gu, Y. W. Du
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  ABSTRACT: The most used method for changing the martensitic transformation temperatures in the ferromagnetic shape memory alloys is tuning the valence election concentration e/a. In this paper, we report an alternative way, i.e., introducing few interstitial boron atoms in Ni43Mn46Sn11 alloy. The experimental results show that the martensitic transformation temperatures increase with the increasing boron content remarkably and large magnetic entropy changes can be obtained in these alloys. A possible origin of the enhanced martensitic transformation temperatures and large magnetic entropy changes is discussed in this paper.
  Applied Physics Letters 03/2008; 92(10):102503-102503-3. · 3.84 Impact Factor
• Article: Large magnetic entropy changes and magnetoresistance in Ni45Mn42Cr2Sn11 alloy

  D. H. Wang, C. L. Zhang, Z. D. Han, H. C. Xuan, B. X. Gu, Y. W. Du
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  ABSTRACT: The magnetic entropy changes and magnetoresistance were studied in Ni45Mn42Cr2Sn11 ferromagnetic shape memory alloy near the martensitic transition temperature. The substitution of Mn by Cr leads to the rapid decrease of the martensitic transition temperature. A large magnetic entropy change, ΔSM, of 15 J/kg K in a magnetic field of 10 kOe and a large negative MR of 45% in a magnetic field up to 50 kOe were observed in this alloy. The temperature and magnetic field induced martensitic transition should be the origin of large ΔSM and MR in Ni45Mn42Cr2Sn11 ferromagnetic shape memory alloy.
  Journal of Applied Physics 01/2008; 103(3):033901-033901-4. · 2.17 Impact Factor
• Article: Soft magnetic properties and microstructure of novel Nb poor Finemet type alloys

  H. S. Liu, C. H. Yin, X. X. Miao, Z. D. Han, D. H. Wang, Y. W. Du
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  ABSTRACT: Series of Nb poor Finemet type alloys were fabricated by substitution of Nb by Al for the first time, and soft magnetic properties of them have been researched by using permeability spectroscopy and X-ray diffraction. It is found that with 0·5 at.-% substitution of Nb by Al, the initial permeability is improved drastically, and the relaxation frequency is enhanced as well, and the loss factor reduces to a very low value of the order of 10−6 in the low frequency range compared to conventional Finemet. The improved soft magnetic properties are related to the lower crystalline anisotropy of FeSiAl compared to FeSi and the proper crystalline volume fraction. This research shows that the substitution of Nb by Al in Nb poor Finemet type alloys can bear ultrasoft magnetic properties at less cost.
  Materials Science and Technology 12/2007; 24(1):45-48. · 0.77 Impact Factor
• Article: Giant low-field magnetic entropy changes in Ni45Mn44−xCrxSn11 ferromagnetic shape memory alloys

  C L Zhang, W Q Zou, H C Xuan, Z D Han, D H Wang, B X Gu, Y W Du
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  ABSTRACT: A series of Ni45Mn44−xCrxSn11 (x = 0, 1, 2) ferromagnetic shape memory alloys were prepared. With slight doping of Cr, the martensitic transition temperatures decrease rapidly. The magnetic entropy changes at a low magnetic field were investigated in these alloys. The maximum value of ΔSM is 23.4 J kg−1 K−1, which was observed in Ni45Mn43CrSn11 alloys. The origin of the magnetic entropy changes in these alloys has been discussed. The giant low-field magnetic entropy changes and low cost make Ni45Mn44−xCrxSn11 alloys a promising candidate for magnetic refrigeration.
  Journal of Physics D Applied Physics 11/2007; 40(23):7287. · 2.54 Impact Factor