YBa2Cu3O7-x涂层导体的外延生长和性能对CeO2缓冲层的依赖性

利用倾斜衬底沉积法在无织构的金属衬底上生长了MgO双轴织构的模板层,在这一模板层上实现了YBa₂Cu₃O_7-x薄膜的外延生长.在外延YBa₂Cu₃O_7-x薄膜前,依次沉积了钇稳定的立方氧化锆和CeO₂作为缓冲层.利用X射线衍射2θ扫描、扫描、Ω扫描和极图分析测定了这些膜的结构和双轴织 关键词： 2Cu₃O_7-x镀膜导体')" href="#">YBa₂Cu₃O_7-x镀膜导体 2缓冲层')" href="#">CeO₂缓冲层 厚度依赖性 外延生长     

NdBa2Cu3O7-δ/YBa2Cu3O7-δ多层膜体系的外延结构和磁通钉扎的研究

采用脉冲激光沉积技术,在单晶SrTiO₃基底上外延生长了一系列名义结构为p×(NdBa₂Cu₃O_7-δ(m)/YBa₂Cu₃O_7-δ(n))的多层膜和准多层膜(单元层NdBa₂Cu₃O_7-δ较厚而YBa₂Cu₃O_7-δ呈非连贯的岛状分布,m,n为激光脉冲数,p为重复周期).样品的超导转变温度在87—91 K范围,具体大小取决于不同的调制结构,多层膜的重复周期越大,层状界面越多,超导转变温度就越低.磁传输测量表明,准多层的样品不仅具有较高的超导转变温度,而且具有较强的磁通钉扎性能,77K零场下的临界电流密度高达4×10⁶ A/cm²,显示出良好的应用前景. 关键词： 2Cu₃O_7-δ')" href="#">NdBa₂Cu₃O_7-δ 多层膜 磁通钉扎 临界电流密度     

Nd-Fe-B/FeCo多层纳米复合膜的结构和磁性

制备了Nd₂₈Fe₆₆B₆/Fe₅₀Co₅₀多层纳米复合磁性薄膜，对溅射态和650℃退火处理15 min试样的相成分分析和微结构的观察显示，溅射态薄膜呈非晶态，经650℃退火处理15 min后，薄膜主要相成分为硬磁性Nd₂Fe₁₄B相和软磁性相FeCo(110)相.Nd₂Fe₁₄B相呈柱状，其易磁化c轴垂直于膜面，尺寸约10 nm.在硬磁性相和软磁性相之间存在少量富Nd相和非晶态，富Nd相大小约7 nm.磁性测量和分析表明，1)该系列薄膜退火态具有垂直于膜面的磁晶各向异性.2)对于固定厚度(10 nm)层Nd-Fe-B和不同厚度(t_FeCo=1—100 nm)层FeCo多层纳米复合膜,剩磁随软磁相FeCo 厚度的增加快速增加，而矫顽力则减小.当t_FeCo=5 nm时，最大磁能积达到200 kJ/m³. 3)硬磁相Nd-Fe-B层和软磁相FeCo层之间交换耦合导致剩磁和磁能积增强. 关键词： Nd-Fe-B/FeCo多层纳米复合膜 交换耦合 磁各向异性     

金属有机物化学气相沉积法生长Ga2（1-x）In2xO3薄膜的结构及光电性能研究

采用金属有机物化学气相沉积（MOCVD）法在蓝宝石（0001）衬底上制备出了Ga_2（1-x）In_2xO₃（x=01—09）薄膜,研究了薄膜的结构、电学和光学特性以及退火处理对薄膜性质的影响.测量结果表明：当In组分x=02时,样品为单斜β-Ga₂O₃结构;x=05的样品,薄膜呈现非晶结构,退火处理后薄膜结构得到明显的改善 关键词： 金属有机物化学气相沉积 2（1-x）In_2xO₃薄膜')" href="#">Ga_2（1-x）In_2xO₃薄膜 蓝宝石衬底 退火     

关于MgB2/Al2O3超导薄膜电阻转变和各向异性的研究

利用电子束蒸发方法将MgB₂超导薄膜沉积到Al₂O₃(001)衬底上.采用标准的四引线法研究了磁场平行和垂直超导薄膜ab平面下的电阻转变.一个激活能模型 U(T,H)=U₀(1-T/(T_c+δ))ⁿ(1-H/H 关键词： 2/Al₂O₃')" href="#">MgB₂/Al₂O₃ 超导体 电阻转变 各向异性     

计算自旋-s算子幺正演化矩阵ds(t)的新方法及其应用

提出了一种严格求解任意自旋-s算子幺正演化矩阵的方法,该方法不同于群论的方法和直接计算的方法,是一种间接的算法.方法的核心是利用两个系统表示的等价性：即自旋-s算子Hamiltonian量H_s=S_x与Heisenberg XX开链带相互作用J_n=n(N-n)的Hamiltonian量的等价性,由于存在这种等价性,自旋-s算子幺正演化矩阵的计算可通过Heisenberg XX开链中态的演化来实现.采用该方法计算了s=3/2,s=2和s=5/2时对应的幺正演化矩阵.由于初始态|sm〉在算子e^-itS_x下的演化实质上相当于对态|sm〉进行一个绕x轴转角为β＝t的转动,演化矩阵元d^s_m'm(t)=〈sm′|e^-itS_x|sm〉就是转动后的态e^-itS_x|sm〉在|sm′〉态上的投影值,所以在t＝π时刻的演化矩阵刚好对应Heisenberg XX开链上量子态的理想传输. 关键词： s算子')" href="#">自旋-s算子 幺正演化矩阵 量子态传输     

宽脉冲中子注入下中子裂变链统计涨落的数值计算

研究了裂变系统在宽脉冲外中子源注入驱动下裂变链统计涨落问题.提出了概率分布W_n方程的分解-合成数值模拟计算方法,使裂变系统注入中子源数值模拟计算扩展到一般广义条件(具有任意时间分布、注入时间零点t₀概率分布函数P(t₀)和数概率分布S(n)等).同时讨论了应用物理模型的等效条件.将基本前提等效条件从单介质区模型扩展到多介质区模型.为解概率分布W_n方程必备参数提供了计算平均公式.     

直流磁控溅射Si和玻璃衬底Fe/Co多层膜的磁性能比较

对直流磁控溅射Si和玻璃衬底［Co_t/Fe_3t］₅(t=2, 3, 4, 5nm)多层膜的磁性能进行了比较.对于t相同但衬底不同的样品，实验发现饱和磁化强度相差很小，但是矫顽力却相差很大.对矫顽力差异的理论分析表明，多层膜的粗糙度和畴壁类型是引起这种差异的主要原因.     

溅射压强对TiN/SiNx纳米多层膜微观结构及力学性能的影响

利用磁控溅射方法在不同溅射压强条件下制备了TiN/SiN_x纳米多层膜.多层膜的微观结构及力学性能分别用X射线衍射仪、原子力显微镜及纳米压痕仪来表征.结果表明随着溅射压强的增大,多层膜的界面变模糊,TiN层的择优取向由(200)晶面过渡到(111)晶面.与此同时,多层膜的表面粗糙度增大,硬度和弹性模量随溅射压强的增大而减小.多层膜力学性能的差异主要是由于薄膜的周期性结构及致密度存在差异所致. 关键词： x多层膜')" href="#">TiN/SiN_x多层膜 界面宽度 表面形貌     

Nin(n≤8)团簇的结构

用高斯程序的B3LYP交换相关函数和全电子基组DGDZVP、TZVP优化Ni_n、Ni_n⁺和Ni_n^-(n=2~8),得到这些体系的基态几何构型、离化能、电子亲和能及键能.结果表明:Ni₂,Ni₃,Ni₄,Ni₅和Ni₆团簇的基态分别是5,7,9,11和13重态.表明:Ni₂,Ni₃,Ni₄,Ni₅和Ni₆团簇中分别有4,6,8,10和12个平行自旋的电子,在每一个Ni_n团簇中非耦合的电子最多,这些电子占据不同的轨道,导致每一个Ni_n团簇的能量最小,说明在这些Ni_n团簇中电子平行的效应大于电子耦合的效应,这显然与d电子的离域效应有关,称为自旋极化效应,符合宏特规则.Ni_n、Ni_n⁺和Ni_n^-(n=2~8)体系的磁矩分别是Ni_n具有8μ_B(n=6~8),Ni_n⁺具有9μ_B(n=6~8),Ni_n具有7μ_B(n=4~8).     

Magnetization reversal and domains structures in (Co/Ni/Co/Pt) multilayers

Multilayers of [Co/Ni(t_Ni)/Co/Pt]_×4 are investigated for different Ni insertion layer thicknesses. The resulting magnetic properties and magnetic domain structures are compared with [Co/Ni]_×8 multilayers. As determined by magneto-optical Kerr effect microscopy and a vibrating sample magnetometer measurements, all multilayers exhibited a perpendicular magnetic anisotropy. It is found that the nucleation field and magnetic coercivity of [Co/Ni(t)/Co/Pt]_×4 multilayers are lower than (Co/Ni)_×8 and decreased with Ni thickness. Magnetization decay measurements reveal that these multilayers did not show an exponential decay behavior as was observed in rare earth transition metal alloys. Very narrow wires will remain stables for several hours even with an applied magnetic field closer to the coercivity. Insertion of very thin Ni in (Co/Pt) multilayers offers a good way to optimize the magnetic properties of the material and adjust the domain size for nanowire-based devices.     

Structure and magnetic properties of wedged Co/Ti multilayers

Co/Ti multilayers with wedge-shaped Co or Ti sublayers were prepared using UHV (5×10⁻¹⁰ mbar) DC/RF magnetron sputtering. The planar growth of the Co and Ti layers was confirmed in situ by X-ray photoelectron spectroscopy. Cobalt sublayers grow on sufficiently thick titanium sublayers in the soft magnetic nanocrystalline phase up to a critical thickness d_crit3.0 nm. For a thickness greater than d_crit, the Co sublayers undergo a structural transition to the polycrystalline phase with much higher coercivity. Furthermore, for the Co/Ti multilayers with nanocrystalline Co sublayers with d_Co=2.7 nm we have observed a significant drop of the coercivity — typically from H_c3.5 kA/m to H_c0.2 kA/m — for Ti thickness d_Ti0.35 nm. The above effect could be explained by the existence of a minimum Ti sublayer thickness (d_min0.35 nm), which is required for the nanocrystalline growth of Co, and/or the formation of quasi-continuous non-magnetic layers for d_Tid_min giving rise to a decrease of the exchange energy between Co sublayers. Magnetic domains and walls studies revealed the structural transitions of the Co sublayers.     

垂直取向FePt/Ag纳米颗粒薄膜的结构和磁性

用磁控溅射法在单晶MgO(100)基片上制备了［FePt 2 nm/Ag dnm］₁₀多层膜， 经真空热处理后，得到具有高矫顽力的垂直取向L1₀-FePt/Ag颗粒膜.x射线衍射结 果表明，在250 ℃的热基片上溅射，当Ag层厚度d=3—11 nm时，FePt颗粒具有很好的［001］取向，随着Ag层厚度的增加，FePt颗粒尺寸减小.［FePt 2 nm/Ag 9 nm］₁₀经过6 00 ℃真空热处理15 min后，颗粒大小仅约8 nm，垂直矫顽力达到692 kA/m.这种无磁耦合作用的颗粒膜，适合用作超高密度的垂直磁记录介质. 关键词： 磁控溅射 垂直磁记录 纳米颗粒膜 0-FePt/Ag')" href="#">L1₀-FePt/Ag     

利用［Fe/Pt］n多层膜降低L10-FePt有序化温度

采用直流磁控溅射方法制备了Fe/Pt多层膜和FePt单层薄膜，再经不同温度真空热处理得到 了有序相L10₀-FePt薄膜.通过x射线衍射谱和磁性研究表明，FePt单层薄膜需 要在500℃ 以上热处理，才能开始有序化转变，而Fe/Pt多层膜可以降低FePt薄膜有序化温度.［Fe(1 5nm)/Pt(15nm)］13₁₃薄膜在350℃热处理后，有序度已经增加到 06，相应矫 顽力达到了501kA/m.多层膜化促进有序化在较低的温度下进行，这是由于热处理过程中多 关键词： 0-FePt有序相')" href="#">L10₀-FePt有序相 磁控溅射 有序度 Fe/Pt多层膜     

Structures and magnetic behaviours of TiO2-Mn-TiO2 multilayers

The TiO2-Mn-TiO2 multilayers are successfully grown on glass and silicon substrates by alternately using radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and the magnetic behaviours of these films are characterised with x-ray diffraction, transmission electron microscope (TEM), vibrating sample magnetometer, and superconducting quantum interference device (SQUID). It is shown that the multi-film consists of a mixture of anatase and rutile TiO2 with an embedded Mn nano-film. It is found that there are two turning points from ferromagnetic phase to antiferromagnetic phase. One is at 42 K attributed to interface coupling between ferromagnetic Mn3O4 and antiferromagnetic Mn2O3, and the other is at 97 K owing to the interface coupling between ferromagnetic Mn and antiferromagnetic MnO. The samples are shown to have ferromagnetic behaviours at room temperature from hysteresis in the M-H loops, and their ferromagnetism is found to vary with the thickness of Mn nano-film. Moreover, the Mn nano-film has a critical thickness of about 18.5 nm, which makes the coercivity of the multi-film reach a maximum of about 3.965×10 2 T.     

Structure of PtFe/Fe double-period multilayers investigated by X-ray diffraction, reflectivity, diffuse scattering and TEM

Double-period [(Pt 1.7 nm/Fe 0.9 nm)₅Fe(t_Fe2)]₈ and [(Pt 1.8 nm/Fe 0.6 nm)₅Fe(t_Fe2)]₈ multilayers with different thickness t_Fe2 (between 0.23 and 4.32 nm) of the additional Fe layers, prepared by combinatorial sputter deposition, show differences in the mosaic spread and the vertical interfacial roughness when deposited on native or thermally oxidised Si wafers. Simulations of the wide-angle X-ray scattering intensities revealed the presence of interdiffusion in the (Pt/Fe)₅ bilayers and systematic variations of the grain sizes, perpendicular to the film surface, as well as the rms variations of the two superlattice periods with the total film thickness. A comparison of ω-rocking scans shows an increase of the correlated vertical roughness of the (Pt/Fe)₅ multilayers with the total multilayer thickness.     

Ag和Ti底层对[Fe/Pt]n多层膜有序化的影响

利用磁控溅射的方法，在热玻璃基片上制备了以Ag，Ti，Cu，Cr，Pt和Ta为底层的［Fe/Pt］_n多层膜，后经不同温度真空热处理，得到L1₀有序结构的FePt 薄膜（L1₀-FePt）.实验结果表明，以Ag和Ti为底层，通过采用基片加温，同时 利用［Fe/Pt］_n多层膜结构，可以促进FePt薄膜的有序化过程，使FePt-L1_０有序化温度从500℃降低到350℃.在较高的温度下退火，以Ag为底层对薄膜的磁性 能影响较小，而以Ti为底层在高于500℃退火后，矫顽力明显下降.在400℃退火20min后，以 Ag和Ti为底层的样品平行膜面的矫顽力分别达到597kA/m和645kA/m，剩磁比分别达到0.81和 0.94，为将来FePt-L1_０有序相合金薄膜用于未来超高密度磁记录介质打下基础. 关键词： ０-FePt薄膜')" href="#">L1_０-FePt薄膜 有序化温度 底层 多层膜结构     

Element-specific magnetization reversal in Fe/Ce multilayers: : a study by X-ray magnetic circular dichroism and the magneto-optic Kerr effect

Fe/Ce multilayers are magnetically soft with coercive fields of a few Oersteds. In this artificial system, the itinerant 5d electrons of Ce are magnetically polarized by hybridization with the spin–split 3d states of Fe. To obtain an insight into the magnetization reversal process, the element selectivity of X-ray magnetic circular dichroism was used to measure the magnetization of the Ce-5d electrons as a function of an applied magnetic field. Comparison with the magnetization curves studied by the magneto-optic Kerr effect, which averages over the whole system, revealed that the coercivity in the hysteresis of the ordered Ce-5d moments is reduced by 50%. We propose that this is an effect of the magnetically disturbed interface or of the complex non-collinear magnetic structure of the Ce layers detected by recent experiments of X-ray resonant magnetic scattering. The results are compared to the X-ray dichroic and Kerr hysteresis loops of the multilayers Fe/La/Ce/La and Fe/CeH_2−δ. These systems are magnetically harder and their coercivities are identical.     

Optical and magnetooptical characterization of FeNi/Cu multilayers

A series of [FeNi(1.7 nm)/Cu(t_Cu)]₃₀/Fe(10 nm) multilayers with the range of t_Cu from 0.36nm to 4.32nm deposited on glass substrates was studied by measuring the effective optical constants n and k, saturation magnetooptical polar Kerr rotation θ _k and ellipticity η_k and evaluating the effective complex off-diagonal elements of the dielectric tensor ε _xy ^′ and ε _xy ^″ . It was found that the four primary quantities ε _xy ^′ , ε _xy ^″ , n and k vary concurrently with respect to t_Cu, while the dependences of θ _k and η _k on t_Cu differ drastically. To explain this difference the contributions of both the real and imaginary parts of the off- diagonal dielectric tensor elements and the effect of complex optical constants have to be considered. No obvious correlation was found between the variation of ñ, ε~ _xy and the oscillations of GMR of the multilayers.