共查询到18条相似文献,搜索用时 93 毫秒
1.
通过X射线衍射及磁测量手段研究了Nd2AlFe12Mn4化合物的热膨胀性质及本征磁致伸缩性质.研究结果表明Nd2AlFe12Mn4化合物在103~654K的温度范围内具有菱方相的Th2Zn17型结构.在183~244K的温度范围内具有负热膨胀性质,其平均热膨胀系数α=-9.01×10-5/K.对本征磁致伸缩的研究结果表明Nd2AlFe12Mn4化合物中存在着较强的各向异性的本征磁致伸缩,103K时其本征体磁致伸缩约为9.3×10-3.磁测量研究结果表明Nd2AlFe12Mn4化合物的居里温度约为210K,比其母合金Nd2AlFe16低约260K,分析认为这是3d次晶格中Mn磁矩与Fe磁矩反铁磁耦合的结果. 相似文献
2.
Er2-xRxFe17(R=Pr,Ce)化合物的结构与磁熵变研究 总被引:1,自引:0,他引:1
在氩保护气氛中用熔炼法制备了Er2-xRxFe17(R=Pr,Ce)系列合金,通过粉末X射线衍射和SQUID磁强计研究了样品的结构和磁熵变.结果表明,轻稀土Pr和Ce的掺入没有明显改变Er2Fe17化合物的相结构,但改变了Er次晶格与Fe次晶格之间的耦合系数,使仍为六方Th2Ni17型结构的Er2-xRxFe17化合物的居里温度可通过成分微调使其处在室温附近,Er2-xRxFe17化合物的λ形(-△SM)-T曲线表明其在居里点附近发生的相变属于二级相变,Er2-xRxFe17化合物有较大的磁熵变,且致冷温区较宽,是一类有很大应用潜力的室温磁致冷材料. 相似文献
3.
热处理温度对TbFe2/Fe交换耦合磁致伸缩多层膜的影响 总被引:5,自引:1,他引:4
采用直流磁控溅射在20mm×5mm×240μm抛光单晶硅片上制备了TbFe2/Fe磁致伸缩多层膜,主要研究了热处理温度对TbFe2/Fe磁致伸缩多层膜磁致伸缩系数的影响.采用量热分析法(DSC)、XPS以及光杠杆测试法对TbFe2/Fe磁致伸缩多层膜的晶化曲线、成分随深度的变化以及磁致伸缩系数进行了分析与测试.结果表明TbFe2薄膜的起始晶化温度为327℃,晶化温度为372℃;TbFe2/Fe磁致伸缩多层膜的最佳热处理温度为327℃,在此热处理温度下热处理60min,外加磁场1.6×104A/m时,TbFe2/Fe磁致伸缩多层膜磁致伸缩系数可达1.56×10-4.采用XPS分析了一个周期的TbFe2/Fe成分随薄膜深度的变化,未经热处理的薄膜Fe层和TbFe2层之间界面清晰,两层之间有少量的扩散.经327℃热处理60min的薄膜Fe层和TbFe2层界面发生了互扩散,原子数之比也发生了改变. 相似文献
4.
用电弧炉熔炼得到Pr0.15Tb0.30
Dy0.55Fe1.85-xNix系列合金.通过X射线对合金进行结构分析,并拟合衍射峰得到晶格常数;样品的居里温度采用交流磁化率测量系统得到;磁化强度、磁致伸缩分别由振动样品磁强计和标准应变测试系统在室温下测量得到.实验表明所有的样品均呈现MgCu2型Laves相结构;随着Ni替代量的增加,样品晶格常数、居里温度和磁化强度呈现下降趋势;磁致伸缩系数亦表现为下降趋势,但在x=0.2、0.3处有所反弹,且x=0.3时样品在低场下的磁致伸缩值略高于无Ni替代的样品. 相似文献
5.
6.
磁致伸缩可作为电磁能和机械能之间的高效转换途径,是基础研究以及技术应用等方面重要的材料性能.然而,在其微观成因的理解方面仍然存在挑战,这对磁致伸缩材料的发展非常重要.本文利用原位磁场和温度场下的粉末中子衍射技术首次揭示了自旋旋转对La(Fe,Al)13超磁致伸缩的关键作用. La(Fe,Al)13超磁致伸缩性能是由磁场驱动的倾斜结构磁矩旋转引起的,其中铁磁成分的急剧增加促使晶格内部二十面体伸长,进而产生巨大的磁致伸缩.此外,本文揭示了La(Fe,Al)13精确的倾斜磁结构特征.本研究提供了一种通过磁场诱导自旋旋转途径探索新型磁致伸缩功能材料的策略. 相似文献
7.
采用熔体快淬法及真空退火工艺制备了Nd9.5Fe76Co5Zr3-xNbxB6.5(x=0~3.0)粘结磁体,研究了其磁性能及温度系数。结果表明,随着Nb含量的增加,合金剩磁逐渐提高,磁能积和矫顽力呈现先增大后减小的趋势。Zr元素与Nb元素复合添加,能够有效地改善矫顽力温度系数β。经最佳条件退火处理后制备的Nd9.5Fe76Co5Zr1.5Nb1.5B6.5的粘结磁体,具有最优的综合磁性能:Br=0.717T,Hcj=773kA/m,(BH)max=82kJ/m3,α20~150℃=-0.111%/℃,β20~150℃=-0.356%/℃。 相似文献
8.
9.
10.
Masayuki Udagawa Yoshinori Nagaoka Norio Ogita Miki Masada Jun Akimitsu Kohji Ohbayashi 《Journal of Superconductivity》1994,7(2):449-451
For Gd2CuO4, a new symmetry-forbidden phonon for the tetragonal T structure is observed. This implies that oxygen in the CuO2 plane is locally distorted along the CuO2 plane. Such distortion has never been observed for other T-type superconductors, which show superconductivity by Ce doping. The disappearance of superconductivity for Gd can be correlated with the appearance of the distortion due to oxygen in the CuO2 plane. 相似文献
11.
12.
New rare earth compounds which are isostructural with silicate minerals of the melilite family have been prepared. The cell dimensions vary linearly with the radii of rare earth ions, showing a typical Lanthanoid contraction. Magnetic susceptibilities of the rare earth compounds were measured in the temperature range from 77 K to 1000 K. A trend toward weak ferromagnetism with decreasing temperature was observed in the heavy rare earth compounds. 相似文献
13.
14.
Crystallization in the systems La2(CO3)3 ⋅ 6H2O-CaCO3(BaCO3)-R-H2O (R = Na2CO3, K2CO3, NaHCO3, KHCO3, NaCl, NH4Cl, CO(NH2)2) was studied under hydrothermal conditions (400–450°C). The solid reaction products were found to contain LaOHCO3 and NaLa(CO3)2. Detailed thermal decomposition schemes were proposed for these phases, and their lattice parameters were refined.
__________
Translated from Neorganicheskie Materialy, Vol. 41, No. 11, 2005, pp. 1366–1372.
Original Russian Text Copyright ? 2005 by Nikol'skaya, Dem'yanets. 相似文献
15.
Ya-Wen Zhang 《Materials Research Bulletin》2004,39(11):1763-1777
By the citrate gel method, (ZrO2)0.85(REO1.5)0.15 (RE = Y, Sc) solid solutions in pure cubic fluorite structure were prepared at relatively low calcination temperatures. The existence of the strong coordination interaction between the COO− groups of the ligands and metal ions could effectively prevent the segregation of metal ions during the gel formation. Upon heat treatment within 110-500 °C, the gel decomposed by multi-steps, with the formation of well-defined intermediate decomposition products, while, the bonding nature between COO− groups and metal ions changed with temperature: unidentate (110-250 °C) → bridging (300-350 °C) → ionic (400-500 °C). The oxide powder resulted from the calcination of the gel at 800 °C is an assembly of mesoporous nanoparticles with uniform sizes, but agglomerated in lumps. It was confirmed that the chemical homogeneity, nanoparticle size uniformity and crystallinity, sinterability and electrical conductivity of (ZrO2)0.85(REO1.5)0.15 can be remarkably improved by avoiding the phase separation (solid/liquid) phenomenon during the preparation of the gels. 相似文献
16.
The stoichiometry and cell parameters of the compounds reported previously as 2R2O3 · 9WO3 were studied with single crystals and sintered samples. They seem to have the title composition and crystallize in an orthorhombic symmetry, Pbcn with Z = 2. The cell parameters are , and for the Nd compound. Cell volumes of these compounds vary linearly with the cube of ionic radius. 相似文献
17.
The synthesis and properties of fluoride glasses in the system ZrF4BaF2GdF3 (or YbF3) are reported. Addition of fluorides of other elements, such as AlF3, PbF2, LaF3 improve glass formation and prevent crystallization. Optical measurements show that these glasses transmit wavelengths up to 8 μm. Doping with PbF2 increases the refractive index from 1.513 to 1.536. 相似文献
18.
A very large forced magnetostriction was observed for Y2 Fe17 and Lu2 Fe17 hexagonal single crystals near their ordering temperatures. The isotropic exchange coefficients are large, compared with the anisotropic terms. These results, which are consistent with the large magnetic volume anomaly observed previously, are interpreted in terms of the dependence of the magnetic interactions on interatomic distance. The largest magnetostriction is measured along the c-axis and a positive sign is observed for (c/a)/(c/a). Both these results are associated with the strong dependence on interatomic distance of the negative interactions occurring in the substitution zones. 相似文献