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利用实验和能带计算相结合的方法,对介于两种预期的半金属Heusler合金Co2FeSi和Co2MnSi间的四元合金Co50Fe25-xMnxSi25的晶体结构、磁性、能带结构和半金属性进行了研究.采用考虑库仑相互作用的的广义梯度近似方法计算了系列合金的能带结构,通过与实验结果进行对比,揭示了成分变化过程中合金分子磁矩及原子磁矩的变化规律.研究发现,
关键词:
磁性
半金属
Heusler合金 相似文献
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聚醚树枝体线性聚(N-异丙基丙烯酰胺)不对称嵌段共聚物的 合成及自组装 总被引:2,自引:0,他引:2
采用原子转移聚合方法合成了聚N-异丙基丙烯酰胺和聚醚树技体的不对嵌段共聚物Dendr.PE-PNI-PAM。实验结果表明Dendr.PE-PNIPAM分子在水中能通过疏水缔合作用形成具有双分子膜结构的超分子聚集体。临界缔合浓度(CAC)、聚集体的大小及形貌对树枝体的代数具有明显的依赖关系。该聚集体对温度刺激具有响应性,并在人体体温温度(37.5℃)发生相转变。在高于相转变温度时,Dendr.PE-PNIPAM分子形成管状、带状等多重形态的超级结构的聚集体。 相似文献
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This paper theoretically investigates the effects of crystal field and exchange interaction field on magnetic properties in dysprosium gallium garnet under extreme conditions (low temperatures and high magnetic fields) based on quantum theory. Here, five sets of crystal field parameters are discussed and compared. It demonstrates that, only considering the crystal field effect, the experiments can not be successfully explained. Thus, referring to the molecular field theory, an effective exchange field associated with the Dy--Dy exchange interaction is further taken into account. Under special consideration of crystal field and the exchange interaction field, it obtains an excellent agreement between the theoretical results and experiments, and further confirms that the exchange interaction field between rare-earth ions has great importance to magnetic properties in paramagnetic rare-earth gallium garnets. 相似文献
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以三聚氯氰为原料合成含醛基的二酚氧基取代中间体(1); 1分别与酚衍生物(2a~2e)经取代反应制得三酚氧基中间体(3a~3e); 3a~3e经缩合、氧化和配位等反应合成了5个新型的含双酚衍生物三枝氟硼二吡咯(BODIPY)荧光染料(4a~4e),其结构经1H NMR, 13C NMR和HR-MS(ESI)表征。4a~4e的最大吸收波长和发射波长分别位于499 nm和508 nm,荧光量子产率为0.41~0.55,显示出BODIPY荧光核典型的光物理性能。 相似文献
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We prepare NiZnFe2O4 soft magnetic ferrites with different molar ratios with the layered precursor method and investigate their magnetic properties. In the layered precursor, metal ions are scattered on the layer plate in a certain way on account of the effect of lowest lattice energy and lattice orientation. After high temperature calcinations, spinel ferrites with uniform structural component and single magnetic domain can be obtained, and the magnetic property is improved greatly. NiZnFe2O4 ferrites prepared have the best specific saturation magnetization of 79.15 emu·g^-1, higher than that of 68 emu·g^-1 prepared by the chemical co-precipitation method and that of 59 emu·g^-1prepared by the emulsion-gel method. Meanwhile the coercivity of NiZnFe2O4 ferrites prepared by layered precursor method is 14 kA·m^-1, lower than that of 50 emu·g^-1 prepared by the co-precipitation method and that of 59 emu·g^-1 prepared by the emulsion-gel method. 相似文献
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运用基于密度泛函理论的第一性原理的方法, 对Ga2基Heusler合金Ga2XCr (X = Mn, Fe, Co, Ni, Cu)的四方畸变、电子结构、磁性及声子谱特性进行了系统的研究. 结果表明, 在保持体积不变的四方畸变中, 五种合金的磁矩主要由Cr元素提供; Ga2FeCr, Ga2CoCr和Ga2CuCr保持稳定的立方相, 而在Ga2MnCr和Ga2NiCr 中观察到能量更低的四方相, 且其能量最低点对应的c/a分别位于1.28和1.11处, 而对应的能量差ΔE 分别为-8.26 meV和-6.14 meV. 电子结构显示, Ga2MnCr和Ga2 NiCr的费米能级附近存在尖锐的电子态密度峰, 导致3d电子能级杂化向宽能量范围扩展, 以消除体系的高能量不稳态, 这个过程导致结构转变的发生. 基于适度的畸变度和能量差, 本文认为Ga2MnCr有存在铁磁马氏体相变的可能, 其声学支虚频的出现, 也进一步表明体系有声子模软化的行为. 相似文献
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凝胶色谱-光散射联用法对壳聚糖及其产品的分子质量及分布的测量 总被引:1,自引:0,他引:1
采用国家基准物质氯化钠和甲苯校准了示差折光仪和增强光系统的仪器常数,用超纯水重量法校准了激光光散射仪到示差检测器之间的延时体积,用葡聚糖标准物质对各角度的光强进行归一化处理,研究了凝胶色谱-激光光散射联用方法中设备的校准和溯源。上述校准途径使仪器溯源到国际SI单位,从而确保了测量结果准确可靠。采用激光光散射仪测得壳聚糖及其产品术后防粘连隔离膜的光折射增量dn/dc值分别为0.118、0.092 mL/g,凝胶色谱-激光光散射联用方法测得壳聚糖及其产品术后防粘连隔离膜的重均分子质量分别为8.897×104、1.168×105g/mol;分子质量分布Mw/Mn分别为1.148±0.026和3.132±0.377。 相似文献
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