脉冲激光沉积制备的Co80Cr20/Ti90Cr10薄膜的结构与磁性

用脉冲激光沉积(PLD)的方法在硅单晶基片上制备了Ti90Cr10和Co80Cr20/Ti90Cr10薄膜,用XRD研究了Ti90Cr10薄膜的晶体结构与制备温度的关系,结果表明随着温度升高,薄膜从非晶态逐步向晶态转化,并且计算了Ti90Cr10薄膜的晶粒大小以及晶格常数.利用透射电镜对Ti90Cr10薄膜进行了表面和截面形貌的表征.采用纳米压痕仪对Ti90Cr10薄膜的硬度和膜基界面结合力进行了分析,表明薄膜的硬度和膜基结合力随制备条件改变有所变化,制备温度增加,薄膜的硬度和膜基结合力随之增加.利用Ti90Cr10薄膜作为中间层,用PLD制备了Co80Cr20磁性层,获得了很好的垂直磁化性质,膜厚减小,矫顽力和矩形比有所增加,600℃真空条件下制备的Co80Cr20(8 nm)/Ti90Cr10(14 nm)薄膜的矫顽力为65.25 kA/m,矩形比为0.86,并且讨论了Co80Cr20/Ti90Cr10薄膜的磁化性质.     

脉冲激光沉积温度及氧压对Bi2Sr2Co2Oy热电薄膜晶体结构与电输运性能的影响

利用脉冲激光沉积技术在c-Al₂O₃单晶基片上制备了Bi₂Sr₂Co₂O_y热电薄膜并研究了沉积温度和氧压对薄膜晶体结构及电输运性能的影响.在最佳沉积条件下制备的单相、c轴取向的Bi₂Sr₂Co₂O_y薄膜的室温电阻率ρ和塞贝克系数S分别为2.9mΩ/cm和110μupV/K,其功率因子S²/ρ好于在单晶样品上得到的值.此外,该薄膜在低温下表现出较强的负磁阻效应,在2K,9T时达到了40%.     

三维海胆状Co3O4的微纳结构制备及锂电池性能

水热法制备的合成海胆状Co₃O₄前驱物在空气中退火得到三维海胆状Co₃O₄的微纳结构. 采用FESEM、TEM、HRTEM以及XRD对产物进行形貌和结构的表征. 结果表明,合成的海胆状结构Co₃O₄由许多粒径约为15 nm的颗粒串接形成. 锂电池测试性能表明,制备的海胆状Co₃O₄首次放电容量达到1.369 Ah/g,经过20次循环     

化学法制备的HfO2薄膜的激光损伤阈值研究

 采用化学法制备了HfO₂介质膜，研究了热处理、紫外辐照以及Al₂O₃复合对HfO₂介质膜激光损伤阈值的影响。采用红外光谱（FTIR）和X射线衍射仪对薄膜进行了表征，并用输出波长为1.064 μm、脉宽为10 ns的电光调Q激光系统测试薄膜的激光损伤阈值。实验结果表明：采用150 ℃左右的温度对薄膜进行热处理可以提高薄膜的激光损伤阈值，所获得的薄膜的激光损伤阈值高达42.32 J/cm²，比热处理前的激光损伤阈值提高了82%；无机材料Al₂O₃的适量添加能够提高薄膜的激光损伤阈值，其中HfO₂与Al₂O₃的最佳质量配比约为95∶5；另外，对薄膜进行适当的紫外辐照也可改善HfO₂ 薄膜以及HfO₂-Al₂O₃复合薄膜的抗激光损伤性能。紫外辐照对提高HfO₂-Al₂O₃复合薄膜的激光损伤阈值效果尤为显著，辐照40 min后的激光损伤阈值达到44.33 J/cm²，比紫外辐照前的激光损伤阈值提高了90%。     

Sr2Bi4Ti5O18的压致结构相变

 使用4∶1的甲醇-乙醇混合液作传压介质，利用金刚石对顶砧装置（DAC），研究了层状铁电体Sr₂Bi₄Ti₅O₁₈的在位高压拉曼光谱和压致结构相变（0～27 GPa）。发现在8.31 GPa，Sr₂Bi₄Ti₅O₁₈经历了一次结构相交。在23.13 GPa以上，Sr₂Bi₄Ti₅O₁₈似乎出现了压致非晶相交的先兆。并使用内模方法对Sr₂Bi₄Ti₅O₁₈的内模进行了指认。     

一维Ni0.5Zn0.5Fe2O4/SiO2复合纳米结构的制备及其磁性能

采用溶胶-凝胶法结合静电纺丝技术制备了Ni_0.5Zn_0.5Fe₂O₄/SiO₂复合纳米纤维.利用热重-差热分析、X射线衍射、场发射扫描电镜、高分辨透射电镜和振动样品磁强计研究了前驱体纤维的热分解及相转化过程以及焙烧温度和SiO₂含量对目标纳米纤维的相组成、微观结构、形貌及磁性能的影响.结果表明,在450 ℃焙烧时,立方尖晶石结构已基本形成.随着焙烧温度由450 ℃升高到100     

Tb2Fe15.5Cr1.5化合物的本征磁致伸缩

通过x射线衍射及磁测量手段研究了Tb₂Fe_15.5Cr_1.5化 合物的热膨胀性质及本征磁致伸缩性质.研究结果表明Tb₂Fe_15.5Cr _1.5化合物在293—672K的温度范围内具有六角相的Th₂Ni_{17型结构.在432—522K的温度范围内具有负热膨胀 性质，其平均热膨胀系数=-157×10^-5/K.对本征磁致伸缩的研究结果表明Tb2Fe15.5Cr1.5化合物中存在着较强的各向异性的本 征磁致伸缩，293K时其本征体磁致伸缩约为84×10^-3，晶格畸变主要发生在c 轴方向上.磁测量研究结果表明Tb2Fe15.5Cr1.5化合物的居里温度约为494K，比其母 合金Tb2Fe17高约80K.}     

Nd掺杂对Bi4Ti3O12铁电薄膜的微结构和铁电性能的影响

利用溶胶-凝胶法在Pt/Ti/SiO₂/Si(100)衬底上制备了Nd掺杂Bi₄Ti₃O₁₂(Bi_4-xNd_xTi₃O₁₂, x=0.00,0.30,0.45,0.75,0.85,1.00,1.50)铁电薄膜样品.研究了Nd掺杂对Bi₄Ti₃O₁₂薄膜的微结构和铁电性能的影响.研究结果表明:Nd掺杂未改变Bi₄Ti₃O₁₂薄膜的基本晶体结构.在掺杂量x<0.45时,Nd³⁺只取代类钙钛矿层中的A位Bi³⁺.当x=0.45时,样品剩余极化强度达最大值,在270kV·cm^-1的电场下为32.7μC·cm^-2.掺杂量进一步增加时,结构无序度开始明显增大,Nd³⁺开始进入(Bi₂O₂)²⁺层,削弱其绝缘层和空间电荷库的作用,导致材料剩余极化逐渐下降.当掺杂量x达到1.50时,掺杂离子最终破坏(Bi₂O₂)²⁺层的结构,材料发生铁电-顺电相变.     

Sb2Te3 纳米结构的制备与表征

以室温热电性能优异的传统热电材料Sb₂Te₃为研究对象,利用化学气相沉积法制备Sb₂Te₃单晶纳米结构,并研究其生长机理.实验结果表明,不加催化剂时Sb₂Te₃易生长成六方纳米盘,在金催化剂条件下定向生长成纳米线.Sb₂Te₃的形貌与其晶体结构和生长机理有关.Sb₂Te₃为三角结构,Sb和     

块状Ta2O5-TiO2复合气凝胶的制备与表征

 以乙醇钽、钛酸丁酯为原料,以乙醇为溶剂,通过溶胶-凝胶法及超临界干燥成功制备了Ta₂O₅-TiO₂复合气凝胶。用场发射扫描电镜（SEM）、透射电镜（TEM）、扫描电镜模式下的电子能谱仪（EDS）以及比表面积吸附仪（BET）对其进行表征。结果表明:该气凝胶是由粒径在nm量级的Ti和Ta的羟基氧化物胶体颗粒堆积而成的低密度、高比表积的多孔网络结构材料,孔径分布主要集中在5~15 nm,比表面积为492.9 m²/g,密度为90 mg/cm³左右。     

大规模制备Ni80Fe20纳米线阵列及其磁学特性研究

利用电化学沉积方法在高度有序纳米孔氧化铝模板中大规模制备了Ni80₈₀Fe 20₂₀纳米线阵列.该方法得到的Ni80₈₀Fe20₂₀ 纳米线产率高（约1012^{12—101313/cm22）, 而且这些纳米线阵列具有（111）择优生 长取向和很高的纵横比.与体材料相比,这些Ni80₈₀Fe20₂₀纳 米线阵列具 关键词： 纳米线阵列 磁性}     

Temperature dependence of the electrical resistivity of amorphous Co80−xErxB20 alloys

The temperature dependence of the electrical resistivity of amorphous Co_80−xEr_xB₂₀ alloys with x=0, 3.9, 7.5 and 8.6 prepared by melt spinning in pure argon atmosphere was studied. All amorphous alloys investigated here are found to exhibit a resistivity minimum at low temperature. The electrical resistivity exhibits logarithmic temperature dependence below the temperature of resistivity minimum T_min. In addition, the resistivity shows quadratic temperature behavior in the interval T_min<T<77 K. At high temperature, the electrical resistivity was discussed by the extended Ziman theory. For the whole series of alloys, the composition dependence of the temperature coefficient of electrical resistivity shows a change in structural short range occurring in the composition range 8–9 at%.     

Effects of oblique-incidence evaporation on magnetic properties of Fe20Ni80/Fe70Co30 bilayer film

Evaporative deposition at oblique incidence is shown to enhance the magnetic anisotropy of an Fe₂₀Ni₈₀ magnetic film and induce magnetic anisotropy in an overlying, strongly isotropic Fe₇₀Co₃₀ film. This deposition method for the formation of an underlayer of several lattice parameters in thickness and semi-hard overlayer of a few thousands Angstroms in thickness achieves a significant change in the magnetization process and strong suppression of the coercive forces of Fe₇₀Co₃₀ in the hard magnetization direction. Soft magnetization of the Fe₇₀Co₃₀ overlayer is not achieved when one of the layers is deposited at oblique incidence. It is anticipated that shape magnetic anisotropy is responsible in part for the magnetic anisotropy induced in both in Fe₂₀Ni₈₀ under- and Fe₇₀Co₃₀ overlayer by oblique incidence evaporation.     

Morphology and magnetic properties of Co0.8Fe2.2O4 films prepared by the chemical solution deposition

Co_0.8Fe_2.2O₄ ferrite thin films have been prepared on Si(0 0 1) substrates by the chemical solution deposition. Structural characteristics indicate all films are single phase with spinel structure and the space group and the mean grain size increases from 8 to 30 nm with the increase of annealing temperature. The magnetic properties of Co_0.8Fe_2.2O₄ thin films are highly dependent on annealing temperature. The sample annealed at 800 °C possesses high saturation magnetization, moderate coercivity and squareness ratio, making it a promising application candidate in high-density record and magneto-optical materials.     

Effect of oxygen pressure on microstructure and magnetic properties of strontium hexaferrite (SrFe12O19) film prepared by pulsed laser deposition

The effects of oxygen pressure during deposition on microstructure and magnetic properties of strontium hexaferrite (SrFe₁₂O₁₉) films grown on Si (100) substrate with Pt (111) underlayer by pulsed laser deposition have been investigated. X-ray diffraction pattern confirms that the films have c-axis perpendicular orientation. The c-axis dispersion (Δθ₅₀) increases and c-axis lattice parameter decreases with increasing oxygen pressure. The films have hexagonal shape grains with diameter of 150-250 nm as determined by atomic force microscopy. The coercivities in perpendicular direction are higher than those in in-plane direction, which shows the films have perpendicular magnetic anisotropy. The saturation magnetization and anisotropy field for the film deposited in oxygen pressure of 0.13 mbar are comparable to those of the bulk strontium hexaferrite. Higher oxygen pressure leads to the films having higher coercivity and squareness. The coercivity in perpendicular and in-plane directions of the film deposited in oxygen pressure of 0.13 mbar are 2520 Oe and 870 Oe, respectively.     

Low-frequency alternative-current magnetic susceptibility of amorphous and nanocrystalline Co60Fe20B20 films

This investigation experimentally studies the low-frequency alternating-current magnetic susceptibility (χ_ac) of amorphous and nanocrystalline CoFeB films by measuring the magnetic field established by passing currents of various frequencies through such films of various thicknesses (t_f). A CoFeB film is sputtered onto a glass substrate with t_f from 100 Å to 500 Å under the following conditions: (a) As-deposited films were maintained at room temperature (RT) and (b) films were post-annealed at T_A=150 °C for 1 h. The samples thus obtained are analyzed in a magnetic field that was generated by an alternating current (AC) at various frequencies from 10 Hz to 25,000 Hz. The experimental results demonstrate that the χ_ac declines as the thickness of the as-deposited sample and the post-annealed sample (T_A=150 °C) increases because the lower coercivity (H_c) of thinner CoFeB films is similar to a soft magnetic characteristic and is associated with a higher χ_ac value. The best χ_ac value is obtained at a thickness of 100 Å under both conditions. The χ_ac value of the post-annealed sample exceeds that of the RT sample at thicknesses from 100 Å to 500 Å because the magneto crystalline anisotropy of the post-annealed sample yields the highest χ_ac value at the optimal resonance frequency (f_res), at which the spin sensitivity is maximal. The X-ray diffraction patterns (XRD) of as-deposited CoFeB films reveal their amorphous structure. The XRD results for the post-annealed films include a main peak at 2θ=44.7° from the body-centered cubic (BCC) nanocrystalline CoFe that indicated a (110) textured structure. Post-annealing treatment caused that the amorphous structure to become more crystalline by a thermally driven process, such that the χ_ac value of the post-annealed sample exceeded that of the RT sample. This experimental result demonstrates that the χ_ac value decreased as the thickness of the thin film increased. Finally, the CoFeB thin films had the best χ_ac at low frequency (<50 Hz) following post-annealing treatment. The results obtained under the two conditions indicate that the maximum χ_ac value and the optimal f_res of a 100 Å-thick CoFeB thin film were 1.6 and 30 Hz, respectively, following post-annealing at T_A=150 °C for 1 h, suggesting that a 100 Å-thick CoFeB thin film that has been post-annealed at T_A=150 °C can be utilized as a gage sensor and in transformer applications at low frequencies.     

The effect of Fe doping on structural and magnetic properties of nanocrystallite Co2Cr1-xFexAl Heusler alloys prepared by mechanical alloying

Mechanical alloying has been used to produce nanocrystallite Co2Cr1-xFexAl(x=0,0.4,0.6,1) Heusler alloys.The formation of the L21 phase of Co2Cr1-xFexAl by the mechanical alloying method was investigated.The effect of Fe doping on the structural and magnetic properties of the samples was also studied.The results were compared with the Slater Pauling prediction.A comparison between these samples and those prepared by the arc-melting method in the literature was made.An increase of the coercivity H c with the increasing Fe doping level was observed.This phenomenon was explained by the increases of lattice strain and magnetic anisotropy with the increasing Fe content.     

低温固相反应法制备的NiFe2O4纳米颗粒的结构与磁性

采用低温固相反应法制备了晶粒尺寸在8—47nm之间的NiFe₂O₄纳米颗粒系列样品，用X射线衍射仪(XRD)、高分辨中子粉末衍射谱仪、振动样品磁强计和超导量子干涉仪等对样品的晶体结构、宏观磁性和纳米颗粒的表面各向异性进行了分析研究.XRD和中子衍射测量结果显示纳米颗粒的晶格常数略高于块体材料，样品的氧参量表明纳米颗粒的晶格畸变程度没有块体材料严重.相对块体材料，纳米颗粒具有较小的磁化强度、较大的矫顽力和各向异性能密度.纳米颗粒从多畴转变为单畴的临界尺寸约为40nm，超顺磁性临界尺寸约为16nm.     

Growth of superconducting FeSe0.5Te0.5 thin films by pulsed-laser deposition

FeSe_0.5Te_0.5 thin films with PbO-type structure are successfully grown on MgO(1 0 0) and LaSrAlO₄(0 0 1) substrates from FeSe_0.5Te_0.5 or FeSe_0.5Te_0.75 polycrystalline targets by pulsed-laser deposition. The film deposited on the MgO substrate (film thickness ∼ 55 nm) shows superconductivity at 10.6 K (onset) and 9.2 K (zero resistivity). On the other hand, the film deposited on the LaSrAlO₄ substrate (film thickness ∼ 250 nm) exhibits superconductivity at 5.4 K (onset) and 2.7 K (zero resistivity). This suggests the strong influence of substrate materials and/or the c-axis length to superconducting properties of FeSe_0.5Te_0.5 thin films.