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Successive phase transformation in ferromagnetic shape memory alloys Co37Ni34Al39 melt-spun ribbons 下载免费PDF全文
The martensitic transformation in Co37Ni34Al29 ribbon is characterized in detail by means of in-situ thermostatic x-ray diffraction and magnetic measurements.The results show a structural transition from the body-centred cubic to martensite with a tetragonal structure during cooling.Comparison between the results of the diffraction intensity with the magnetic susceptibility measurements indicates that the martensitic transformation takes place in several different steps during cooling from 273 to 163 K.During heating from 313 to 873 K,the peak width becomes very wide and the intensity turns very low.The γ-phase(face-centred cubic structure) emerges and increases gradually with temperature increasing from 873 to 1073 K. 相似文献
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Giant reversible magnetocaloric effects and magnetic properties in Eu_(0.9)R_(0.1)TiO_3 (R = La, Ce) are investigated. The antiferromagnetic ordering of pure Eu TiO_3 can significantly change to be ferromagnetic as substitution of La(x = 0.1)and Ce(x = 0.1) ions for Eu~(2+) ions. The values of-?S_M and RC are evaluated to be 10.8 J/(kg·K) and 51.8 J/kg for Eu_(0.9)Ce_(0.1)TiO_3 and 11 J/(kg·K) and 39.3 J/kg for Eu_(0.9)La_(0.1)TiO_3 at a magnetic field change of 10 kOe, respectively. The large low-field enhancements of-?S_M and RC can be attributed to magnetic phase transition. The giant reversible MCE and large RC suggest that Eu_(0.9)R_(0.1)TiO_3 (R = La, Ce) compounds could be promising materials in low temperature and low magnetic field refrigerants. 相似文献
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The magnetic properties and magnetocaloric effect(MCE) in EuTi_(1-x)Co_xO_3(x = 0, 0.025, 0.05, 0.075, 0.1) compounds have been investigated. When the Ti~(4+) ions were substituted by Co2+ions, the delicate balance was changed between antiferromagnetic(AFM) and ferromagnetic(FM) phases in the EuTiO_3 compound. In EuTi_(1-x)Co_xO_3 system, a giant reversible MCE and large refrigerant capacity(RC) were observed without hysteresis. The values of -?S_M~(max) were evaluated to be around 10 J·kg~(-1)·K~(-1) for EuTi_(0.95)Co_(0.05)O_3 under a magnetic field change of 10 kOe. The giant reversible MCE and large RC suggests that EuTi_(1-x)Co_xO_3 series could be considered as good candidate materials for low-temperature and low-field magnetic refrigerant. 相似文献
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Magnetic properties and magnetocaloric effect of compound PrFe 12 B 6 are investigated.The coexistence of hard phase PrFe 12 B 6 and soft phase α-Fe causes interesting phenomena on the curves for the temperature dependence of magnetization.PrFe 12 B 6 experiences a first order phase transition at the Curie temperature 200 K,accompanied by an obvious lattice contraction,which in turn results in a large magnetic entropy change.The Maxwell relation fails to give the correct information about magnetic entropy change due to the first order phase transition nature.The large magnetic entropy changes of PrFe 12.3 B 4.7 obtained from heat capacity method are 11.7 and 16.2 J/kg.K for magnetic field changes of 0-2 T and 0-5 T respectively. 相似文献
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利用x射线衍射及磁测量手段研究了Ho2AlFe16-xMnx系列化合物的结构.结果表明,该系列化合物具有Th2Ni17型结构;随着x的增加,化合物的单胞体积呈现非线性的变化,结合磁测量结果分析认为,在化合物的磁相变点附近存在较大的正的本征磁致伸缩.在160—285K温度范围内对Ho2AlFe14Mn2化合物进行的变温x射线衍射研究表明,该化合物在其居里点附近(220—270K)具有负热膨胀性质,其平均热膨胀系数为-14×10-4/K.
关键词:
Ho2AlFe16-xMnx化合物
负热膨胀
本征磁致伸缩 相似文献