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Enke Liu,
Wenhong Wang,
Lin Feng,
Wei Zhu,
Guijiang Li,
Jinglan Chen,
Hongwei Zhang,
Guangheng Wu, Chengbao Jiang,
Huibin Xu,
Frank de Boer
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ABSTRACT: The magnetostructural coupling between the structural and the magnetic transition has a crucial role in magnetoresponsive effects in a martensitic-transition system. A combination of various magnetoresponsive effects based on this coupling may facilitate the multifunctional applications of a host material. Here we demonstrate the feasibility of obtaining a stable magnetostructural coupling over a broad temperature window from 350 to 70 K, in combination with tunable magnetoresponsive effects, in MnNiGe:Fe alloys. The alloy exhibits a magnetic-field-induced martensitic transition from paramagnetic austenite to ferromagnetic martensite. The results indicate that stable magnetostructural coupling is accessible in hexagonal phase-transition systems to attain the magnetoresponsive effects with broad tunability.
Nature Communications 01/2012; 3:873. · 7.40 Impact Factor
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ABSTRACT: The reverse martensitic transformation was monitored by testing the x-ray diffraction patterns with increasing temperatures in an Ni46Mn33Ga17Cu4 alloy. A large magnetization change from a weak-magnetic martensite phase to a ferromagnetic austenite phase has been found on the M–T curves of heating cycle in this alloy. The reverse martensitic transformation temperatures have been lowered by 7 K under the magnetic field of 90 kOe. The magnetic field-induced reverse martensitic transformation has been confirmed at a fixed temperature in this alloy, demonstrating that another alloy performing the MFIRMT is discovered: NiMnGaCu alloy.
Journal of Physics D Applied Physics 06/2011; 44(28):285002. · 2.54 Impact Factor
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ABSTRACT: The magnetostriction curves and minor loops of the TbDyFe [110] oriented crystal are tested under different compressive pre-stress from 0 to 120 MPa. It is observed that the magnetostriction hysteresis first increases from about 33 Oe under 0 MPa, achieves the maximum of about 70 Oe under 30 MPa, and then decreases to about 16 Oe under 120 MPa (near disappearance) with an increase in the compressive pre-stress. By the theoretical simulation, it is found that upon increasing the compressive pre-stress the dominant energy changes from magnetocrystalline anisotropy energy to magnetoelastic energy. This leads to the domain rotation mode changing from irreversibility to reversibility and consequently results in the decrease of magnetostriction hysteresis, which explains the experimental results very well.
Journal of Applied Physics 06/2011; 109(12):123923-123923-5. · 2.17 Impact Factor
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ABSTRACT: The magnetostriction curve of [110]-oriented Tb0.3Dy0.7Fe1.9 crystal is measured under different compressive prestress. It is observed that the saturation magnetostriction keeps on increasing with the increase in compressive prestress from 0 to 75 MPa. The distribution of the free energy within the (110) plane normal to the stress axis is calculated to clarify the enhancement of saturation magnetostriction under large compressive prestress. It is found that with the increase in the prestress, the lowest energy positions deviate from the initial four 〈111〉 easy axes in the (110) plane, approaching the [10] and [10] orientations. The stress-induced anisotropy results in the change in initial domain configuration and further the enhancement of saturation magnetostriction, which well explains the experimental results.
Journal of Applied Physics 09/2010; 108(6):063908-063908-4. · 2.17 Impact Factor
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ABSTRACT: Seeking high precision actuator and transducer materials potentially applied under high load remains active in recent years. Magnetostrictive property, magnetostriction saturation field HS, and pizeomagnetic coefficient d33 are investigated in Fe81Ga19 alloy under high compressive prestress. The measured saturation magnetostriction remains above 300 ppm in the 〈001〉 oriented Fe81Ga19 polycrystalline rod under high compressive prestress up to 431 MPa. Two-stage phenomenon was observed in curves plotted for HS and d33 against compressive prestress σ. The domain rotation path and magnetostriction under different compressive prestress are simulated, and this helps to deeply understand the tested magnetostriction. Based on the simulation, the mathematical equations of HS-σ and d33-σ were established for Fe–Ga 〈001〉 oriented crystal revealed two mechanisms, which satisfy proposed functions of experimental data. The high magnetostriction and low saturation field under high prestress indicate that Fe–Ga alloy is possible to be a sound candidate for high load application.
Journal of Applied Physics 08/2010; 108(3):033913-033913-6. · 2.17 Impact Factor
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ABSTRACT: The effect of Fe substitution on the phase transformation and magnetic properties of Mn <sub>2</sub> NiGa has been studied. A single bcc phase was obtained in Mn <sub>2-x</sub> Fe <sub>x</sub> NiGa (x=0–0.6) . With the substitution of Fe for Mn, the lattice constant decreases gradually. The martensitic transformation can be observed when x=0–0.3 . Both the martensitic transformation and austenitic transformation temperatures decrease monotonically with increasing Fe content, which is different from common electron concentration dependence in Ni–Mn–Ga system. The saturation magnetizations M<sub>s</sub> of Mn <sub>2-x</sub> Fe <sub>x</sub> NiGa in both austenitic and martensitic phases increase obviously with the doping of Fe, while the variation of T<sub>C</sub> shows an opposite tendency. Theoretical calculations indicate that both austenitic and martensitic phases are ferrimagnets. The Fe moment varies from positive to negative after the tetragonal distortion, which leads to the decrease of the saturation magnetization.
Journal of Applied Physics 02/2010; · 2.17 Impact Factor
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ABSTRACT: Search for transformation from paramagnetic martensite to ferromagnetic austenite in ferromagnetic shape memory alloys is performed through designing NiMnGaCu alloys. The composition dependence of the martensitic transformation temperature T<sub>M</sub> , the magnetic transition temperatures T<sub>C</sub><sup arrange="stagger">A</sup> of the austenite and T<sub>C</sub><sup arrange="stagger">M</sup> of the martensite is systematically investigated. The sequence of the martensitic transformation and magnetic transition is determined. The diagram on the structural and magnetic transition in a specific system Ni <sub>46</sub> Mn <sub>25+x</sub> Ga <sub>25-x</sub> Cu <sub>4</sub> is outlined, in which a transformation from paramagnetic martensite to ferromagnetic austenite is predicted, exhibiting T<sub>C</sub><sup arrange="stagger">M</sup>≪T<sub>M</sub>≪T<sub>C</sub><sup arrange="stagger">A</sup> . Such a transformation is then experimentally achieved in Ni <sub>46</sub> Mn <sub>33</sub> Ga <sub>17</sub> Cu <sub>4</sub> alloy.
Applied Physics Letters 08/2009; · 3.84 Impact Factor
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ABSTRACT: A Mn-based Heusler alloy Mn <sub>2</sub> NiSb has been synthesized. First-principles calculations and experimental measurements were employed to investigate its electronic structure and magnetism. Theoretical calculation indicates a ferromagnetic coupling in Mn <sub>2</sub> NiSb and a total spin moment of 4.21μ<sub>B</sub>/ f .u . , which agrees quite well with the saturation moment at 5 K. This ferromagnetic coupling arises from the larger lattice constant and more valence electrons compared with other Mn-based Heusler alloys. The partial spin moments for Mn (A) , Mn (B) , and Ni are 0.6, 3.30, and 0.3μ<sub>B</sub> , respectively. The Curie temperature of Mn <sub>2</sub> NiSb is 647 K, indicating a strong exchange interaction between Mn atoms.
Journal of Applied Physics 06/2009; · 2.17 Impact Factor
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ABSTRACT: Magnetostriction behaviour and magnetostriction hysteresis of the single crystal alloy Tb0.29Dy0.48Ho0.23Fe2 are investigated experimentally and theoretically. The oriented 1 1 0 single crystals of the magnetostrictive alloy Tb0.29Dy0.48Ho0.23Fe2 are successfully prepared by the optical floating zone melting method. The single crystals are characterized by optical metallography, x-ray diffraction and x-ray Laue back-reflection measurement. The giant magnetostrictive properties are achieved in a wide operating temperature range from −60 to 80 °C. The calculated magnetostriction of the present alloy is reduced by only 6%, but the magnetostriction hysteresis (Wh) is reduced by more than 30%, compared with the traditional Terfenol-D giant magnetostrictive alloy. The magnetostriction behaviour is modelled using phenomenological theory. The rotation paths of magnetic domain moments are mathematically calculated and hence the resultant magnetostriction is obtained. The theoretical model of magnetostriction hysteresis Wh is proposed and the intrinsic factors of Wh are determined, which can well explain the pre-stress and temperature dependence of magnetostriction hysteresis.
Journal of Physics D Applied Physics 07/2008; 41(15):155012. · 2.54 Impact Factor
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ABSTRACT: The site preference of 3d atoms Y in Mn2YAl (Y = V, Fe, Co) alloys and its influence on their electronic structures and magnetism have been studied by first-principles calculations. The results prove that elements with more valence electrons than Mn tend to enter the A (0, 0, 0) and C (½, ½, ½) sites and elements with fewer electrons prefer the B (¼, ¼, ¼) site (Wyckoff positions). Meanwhile, it is found that for Mn2VAl and Mn2FeAl, a high spin polarization can be obtained whether the Y atom enters the (A, C) or the B site. In particular, Mn2VAl is half-metallic whether it forms the Cu2MnAl type or the Hg2CuTi type of structure. And a 100% spin polarization can be retained even when a 25% Mn–V antisite disorder occurs. This is quite preferable in practical applications. It is also found that the higher-valent element such as Co at the B (¼, ¼, ¼) site has opposite effects and tends to close the energy gap. Finally, a systemic summarization on the electronic and magnetic properties of Mn2YAl (Y = Ti, V, Cr, Mn, Fe and Co) alloys was made. All of them except for Mn2TiAl are predicted as half-metals. The calculated total spin moment is an integral value and increases from −3µB/f.u. for Mn2TiAl to +2µB/f.u. for Mn2CoAl with increasing number of valence electrons. This agrees with the Slater–Pauling curve quite well. All the Mn2YAl alloys studied here are ferrimagnets.
Journal of Physics D Applied Physics 02/2008; 41(5):055010. · 2.54 Impact Factor
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ABSTRACT: Magnetic heat treatment has been carried out on a giant magnetostrictive alloy Tb0.36Dy0.64(Fe0.85Co0.15)2 with ⟨110⟩ crystal orientation. A dramatic improvement in magnetostriction along and perpendicular to the crystal axis (defined as λ‖ and λ⊥, respectively) occurs when cooling the sample through the Curie temperature TC under 240 kA/m applied perpendicular to its axis. When the applied annealing field was parallel to the crystal axis, the magnetostrictive behavior becomes “anomalous;” negative λ‖ and positive λ⊥ are obtained in low fields, accompanied with relatively low values in high fields. A single-{111}-twin model has been suggested to explain such differential magnetostrictive response.
Applied Physics Letters 03/2007; 90(10):102502-102502-3. · 3.84 Impact Factor
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ABSTRACT: Magnetostriction and the electrical resistivities of as-cast and ⟨110⟩ oriented crystals of Tb0.3Dy0.7(Fe1−xSix)1.95 (x = 0,0.025,0.1) were investigated. Giant magnetostriction and obvious magnetostrictive jump effect were observed in oriented Si doped TbDyFeSi crystals especially for x = 0.025. The electrical resistivities of both as-cast and ⟨110⟩ oriented TbDyFeSi were studied at the temperature range from 250 to 300 K. Drastic increases of resistivity were observed in the as-cast Si doped TbDyFeSi magnetostrictive alloys with the increase ratios of 66% and 97% for x = 0.025 and 0.1, respectively, compared with traditional Tb0.3Dy0.7Fe1.95 alloy. The electrical resistivities of oriented alloys are slightly smaller in comparison with that of the as-cast ones.
Applied Physics Letters 11/2006; 89(19):192507-192507-3. · 3.84 Impact Factor
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ABSTRACT: The magnetomechanical damping capacity of the giant magnetostrictive Tb <sub>0.36</sub> Dy <sub>0.64</sub>( Fe <sub>1-x</sub>T<sub>x</sub>)<sub>2</sub> ( x=0 , 0.05, 0.10; T= Mn or Co) alloys has been calculated from quasistatic strain-stress hysteresis loops at room temperature. Stress ranges from 0 to 10, 20, 30, and 50 MPa were used in a series of applied fields between 0 and 3250 Oe . The largest damping capacities were obtained at zero field with values of 1.14 for Tb <sub>0.36</sub> Dy <sub>0.64</sub> Fe <sub>2</sub> , 1.62 for Tb <sub>0.36</sub> Dy <sub>0.64</sub>( Fe <sub>0.95</sub> Mn <sub>0.05</sub>)<sub>2</sub> , and 1.84 for Tb <sub>0.36</sub> Dy <sub>0.64</sub>( Fe <sub>0.90</sub> Co <sub>0.10</sub>)<sub>2</sub> , respectively. In low fields, the damping capacity ΔW/W decreases drastically with the applied stress and magnetic field. However, in higher fields, ΔW/W decreases slightly with the magnetic field but only increases slightly with the applied stress. The results show that both Mn and Co as substitutes for Fe are beneficial for obtaining higher damping capacity.
Journal of Applied Physics 08/2006; · 2.17 Impact Factor
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ABSTRACT: Giant magnetostrictive alloy (GMA) actuators are tending to replace piezoelectric actuators in many applications owing to their giant magnetostrain and fast response. In an active vibration control system using GMA actuators, the investigation of dynamic magnetostrain can supply the basis for the optimization of actuator designs and control algorithms. Experiments have been carried out under varied operating conditions. The results show that there is a better dynamic output only at suitable prestress and magnetic bias values. For a fixed frequency, the output is basically proportional to the input amplitude but the inclination is slightly different for each input frequency. The natural frequency of the actuator is around 5 Hz and the output displacement decreases with frequency increase after 10 Hz. The dynamic magnetostrain at the natural frequency can be larger than the quasi-static value by up to 40%.
Smart Materials and Structures 07/2005; 14(4):N38. · 2.09 Impact Factor
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ABSTRACT: The temperature dependence of the magnetostrain was investigated in the Ni <sub>50</sub> Mn <sub>27.5</sub> Ga <sub>22.5</sub> magnetic shape memory alloy with a five-layer martensitic (5M) structure in the temperature range from 110 K to 300 K . A temperature threshold at 166 K was found for the magnetostrain. A giant magnetostrain of 6.3% was achieved above the temperature, while no magnetostrain was monitored below the temperature. No intermartensitic transformation was detected around the temperature threshold. The lattice parameter a slightly increases, c largely decreases, and the tetragonality (a/c-1) drastically increases with decreasing the temperature. The increase of the tetragonality is thought to be related to the temperature threshold of the magnetostrain by inducing a change of the electronic structure, twin structure, or the type of the variant with the same 5M martensitic structure below the temperature threshold. The interpretation is reasonably understood by the fact that only few samples with the same 5M martensitic structure exhibit a giant magnetostrain.
Applied Physics Letters 07/2005; · 3.84 Impact Factor
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ABSTRACT: Giant magnetostrictive actuators are designed and fabricated with home-made TbDyFe magnetostrictive rods. The corresponding static and dynamic characteristics are tested. The total output displacement can be obtained up to 100 µm and the output force up to 1500 N. The dynamic responses of input and output are accordant and have a small hysteresis. Experiments on active vibration control are implemented in single-degree-of-freedom (DOF) and six-DOF platforms in a flexible space structure. The excellent damping effect, up to 30 dB, proves the good performance of the actuators, the feasibility of the control algorithms, and the reasonable design of the six-DOF platform.
Smart Materials and Structures 04/2004; 13(3):473. · 2.09 Impact Factor
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ABSTRACT: A high-temperature shape-memory alloy, Ni <sub>54</sub> Mn <sub>25</sub> Ga <sub>21</sub>, was developed with a shape-memory effect of 6.1% and a martensitic transformation temperature higher than 250 °C for single crystals. The measured compressive strength and strain were 845 MPa and 20.5%, respectively, with a compressive axis along the growth direction of the rods at room temperature. One thousand thermal cycles were performed on the Ni <sub>54</sub> Mn <sub>25</sub> Ga <sub>21</sub> without obvious changes of the martensitic structure, transformation behavior, and shape-memory effect, indicating an excellent thermal stability for the present alloy. © 2003 American Institute of Physics.
Applied Physics Letters 06/2003; · 3.84 Impact Factor
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ABSTRACT: Superhigh strains of 15% for the Ni53Mn25Ga22 and 13.5% for the Ni54Mn23Ga23 with the nonmodulated martensite structure were achieved by variant reorientation. A strong magnetic anisotropy exists in the prefabricated single variant with the easy axis along the contraction [001] direction of the high-temperature cubic phase. A higher austenitic transformation temperature was found in the single variant comparing with the original multivariant sample. The same order of magnitude for the saturation magnetization Ms, magnetic anisotropy constant ku, and the twin reorientation stress σtw, namely, 57.6 A m2/kg, 1.4×105 J/m3, and approximately 20 MPa, respectively, as those in 5M martensite indicate that it is reasonable to expect a much higher magnetic field-induced-strain in the nonmodulated NiMnGa alloys. © 2002 American Institute of Physics.
Applied Physics Letters 10/2002; 81(15):2818-2820. · 3.84 Impact Factor
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ABSTRACT: A co-occurrence of magnetic and structural transitions was observed in a nonstoichiometric Ni53Mn25Ga22 alloy which undergoes a reverse martensitic transformation from ferromagnetic martensite to paramagnetic austenite at a magnetic transition temperature (134 °C) higher than the Curie temperature of the stoichiometric Ni2MnGa alloy (103 °C). The effect of the magnetic field on the phase transition temperature was found to be two orders of magnitude greater in the present alloy than in Ni2MnGa due to the absence of the ferromagnetic state in austenite. This may open the possibility of utilizing NiMnGa alloys at a low magnetic field. © 2002 American Institute of Physics.
Applied Physics Letters 03/2002; 80(9):1619-1621. · 3.84 Impact Factor
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ABSTRACT: The Ti50Ni48Fe2 alloy was deformed at low temperature (−70°C) and ambient temperature, where the initial states of the samples were pure martensitic phase or austenitic, respectively. The shape memory effect and the reverse transformation temperature were studied on the samples deformed at different temperatures. A maximum shape recovery strain of 5.6% was obtained and the As′ point of the samples deformed at low temperature was raised by about 40°, while a recovery strain of 4% was obtained and the As″ was raised by 55°, rising up to 35°C, in the samples deformed at ambient temperature. An access was approached to the pre-deformation, storage, transportation and installation of components made of Ti50Ni48Fe2 alloy at ambient temperature.
Materials Science and Engineering: A. 281:234-238.
