GdFeCo/AIN/TbFeCo薄膜的变温磁化性能研究

用磁控溅射法制备了GdFeCo/AlN/TbFeCo静磁耦合多层薄膜.振动样品磁强计和克尔磁滞回线测试装置的测试结果表明:25℃不加外磁场时GdFeCo/AlN/TbFeCo静磁耦合多层薄膜读出层(GdFeCo)的极向克尔角为零,读出层呈平面磁化;125℃不加外场时读出层的克尔角最大(O.54°),读出层的磁化方向为垂直磁化;随着温度增高,读出层由平面磁化转变为垂直磁化,在75℃到125℃温度范围内读出层磁化方向很快从平面磁化转变为垂直磁化.对磁化过程的机理研究表明:饱和磁化强度和有效各向异性常量影响读出层磁化方向的转变过程,但主要受读出层饱和磁化强度的影响;在较高温度时读出层的磁化强度较小,退磁场能较小,在静磁耦合作用下,使GdFeCo读出层的磁化方向发生转变.制备的GdFeCo/AlN/TbFeCo静磁耦合多层薄膜适合作CAD-MSR记录介质.     

GdFeCo/AlN/TbFeCo薄膜的变温磁化性能研究

用磁控溅射法制备了GdFeCo/AlN/TbFeCo静磁耦合多层薄膜。振动样品磁强计和克尔磁滞回线测试装置的测试结果表明 :2 5℃不加外磁场时GdFeCo/AlN/TbFeCo静磁耦合多层薄膜读出层 (GdFeCo)的极向克尔角为零 ,读出层呈平面磁化 ;12 5℃不加外场时读出层的克尔角最大 (0 .5 4°) ,读出层的磁化方向为垂直磁化 ;随着温度增高 ,读出层由平面磁化转变为垂直磁化 ,在 75℃到 12 5℃温度范围内读出层磁化方向很快从平面磁化转变为垂直磁化。对磁化过程的机理研究表明 :饱和磁化强度和有效各向异性常量影响读出层磁化方向的转变过程 ,但主要受读出层饱和磁化强度的影响 ;在较高温度时读出层的磁化强度较小 ,退磁场能较小 ,在静磁耦合作用下 ,使GdFeCo读出层的磁化方向发生转变。制备的GdFeCo/AlN/TbFeCo静磁耦合多层薄膜适合作CAD MSR记录介质     

GdFeCo/DyFeCo交换耦合两层薄膜磁化方向转变的研究

用磁控溅射法制备了GdFeCo/DyFeCo交换耦合两层薄膜，对交换耦合两层薄膜变温磁化方向进行了研究.结果表明读出层GdFeCo随温度上升从平面磁化转变成垂直磁化，转变过程中主要受饱和磁矩(M_s)的影响.在GdFeCo的补偿温度附近，读出层的磁化强度近于零，退磁场能减小，并在交换耦合的作用下，使读出层的磁化方向发生转变，制备的交换耦合两层薄膜具有中心孔磁超分辨效应. 关键词： 磁光记录 交换耦合两层薄膜 磁化     

Temperature—Induced Magnetization Reorientation in GdFeCo／TbFeCo Exchange—Coupled Double Layer Films

GdFeCo/TbFeCo exchange-coupled double-layer (ECDL) films used /or centre aperture type magnetically in-duced super resolution were investigated through experiments and theoretical calculation. The ECDL films were prepared by the magnetron sputtering method. Polar Kerr effect measurements showed that magnetization reorientation occurred in the GdFeCo layer with the temperature rising, which was subsequently analysed by the micromagnetic calculation based on the mean-field theory and a continuum model. Theoretical analysis is in agreement well with the experimental results.     

磁光型记录介质疲劳特性研究

本文对单层结构和多层结构磁光型记录介质的疲劳特性进行研究,并对记录介质化学稳定性、记录介质循环擦写后记录磁畴物理特性及磁光记录动态特性载噪比和误码率进行分析,最后对磁光型记录介质的疲劳特性和信息记录可靠性进行评价。     

Cu添加石榴石磁光薄膜读,写性能的研究

用热分解法在玻璃衬底上制备了Ｃｕ添加的Ｂｉ，Ａｌ：ＤｙＩＧ磁光薄膜，对其静态读、写性能进行了详细的研究。Ｃｕ添加的薄膜可获得高的矫顽力和好的矩形化，对记录畸起着稳定的作用。同时，适量Ｃｕ的添加可起到细化晶粒的作用，对减少晶界噪声有利。     

一种新的超分辨记录点的读出技术

提出一种新的超分辨记录点的读出技术—超分辨反射膜技术，详细分析了其原理。用该技术，以Sb为超分辨反射膜，SiN为介电层，在激光波长为632．8nm和光学头的数值也径为0．40的读出光学系统中实现了直径为380nm的超分辨记录点的读出。同时研究了Sb薄膜厚度对读出信噪比的影响规律，发现最佳的Sb薄膜厚度为28～30nm，所得的信噪比为38～40dB。     

大尺寸Bi、Al替DyIG磁光膜的均匀性研究

首先应用磁介质中的传输矩阵处理方法建立分层磁光介质材料中耦合法拉第角的计算模型,其次用热分解工艺制备出分层Bi、Al替DyIG磁光薄膜。经测试发现分层工艺对膜面各点的法拉第角有极大影响,其法拉第角差别在±0.5°左右,采用加热连续涂布及快速循环退火可使不均匀性大大降低。     

GdFeCo磁光薄膜中RE-TM反铁磁耦合与激光感应超快磁化翻转动力学研究

使用飞秒时间分辨抽运-探测磁光克尔光谱技术,研究了激光加热GdFeCo磁光薄膜跨越铁磁补偿温度时稀土-过渡金属(RE-TM)反铁磁交换耦合行为和超快磁化翻转动力学. 实验观察到由于跨越铁磁补偿温度、净磁矩携带者交换而引起的磁化翻转反常克尔磁滞回线以及在同向外磁场下,反常回线上大于和小于矫顽力部分的饱和磁化强度不同,显示出GdFeCo中RE与TM之间的非完全刚性反铁磁耦合. 在含有Al导热底层的GdFeCo薄膜上观测到饱和磁场下激光感应磁化态翻转及再恢复的完整超快动力学过程. 与剩磁态的激光感应超快退磁化过 关键词： 补偿温度 磁化翻转 反铁磁耦合 GdFeCo     

等宽圆环光瞳滤波器的超分辨性能研究

设计一种等宽圆环光瞳滤波器 ,并研究了它的超分辨性能。分析了光瞳中心半径和圆环数对斯特耳比、超分辨能力和旁瓣强度的影响 ,讨论了设计等宽圆环光瞳滤波器时中心半径和圆环数的优化问题。表明圆环数为奇数和偶数时 ,光瞳具有不同的超分辨性能 ;圆环数分别取 1和 2时 ,综合考虑超分辨性能较佳     

红敏聚乙烯醇/丙烯酰胺体系光致聚合物全息记录材料的空间分辨力增强研究

针对目前聚乙烯醇/丙烯酰胺体系光致聚合物材料的空间分辨力不高的问题,提出了一种采用低相对分子质量的聚乙烯醇作为成膜剂来改进光致聚合物分辨力的新方法.采用不同相对分子质量(72000,15000,9000)的聚乙烯醇成膜剂制成光致聚合物,对其衍射效率和空间分辨力等指标进行了对比实验.实验表明选用低相对分子质量(9000)的成膜剂可将该体系光致聚合物的分辨力提高到3000 line/mm以上,实验中仅需40 mJ/cm2左右的曝光量即可获得85%的衍射效率.另外,还对该材料的全息存储特性及其在角度复用全息存储方面的初步应用结果进行了报道.     

Theory for the Exciton Magnetic Polaron in Diluted Magnetic Semiconductors with Thermodynamic Fluctuations of Magnetization

The photoinduced self-trapped exciton magnetic polaron (ST-EMP) in diluted magnetic semiconductors has been the subject of intensive investigations related to the observed photoluminescence during the last two decades. The stability, however, seems still controversial. In this article we study the stability of ST-EMP theoretically, including thermodynamic fluctuations of magnetization. The calculation suggests that the EMP in CdTe(Mn) (Mn: 10-20%) is not self-trapped except at low temperatures below ¨ 1 K, but the other primary localization mechanisms, for example, alloy potential fluctuations, are necessary to the localization of EMP above ¨ 1 K.     

Magnetic field synthesis of Fe3O4 nanoparticles used as a precursor of ferrofluids

Methods to synthesize magnetic Fe₃O₄ nanoparticles and to modify the nanoparticle surface are presented in this paper. In these methods, Fe₃O₄ nanoparticles were prepared by co-precipitation, and the aging of nanoparticles was improved by applied magnetic field. The obtained nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and vibrating sample magnetometer (VSM). Thereafter, to enhance the compatibility between nanoparticles and water, an effective surface modification method was developed by grafting acrylic acid onto the nanoparticle surface. FT-IR, XRD, transmission electron microscopy (TEM), and thermogravimetry (TG) were used to characterize the resultant sample. The testing results indicated that the polyacrylic acid chains have been covalently bonded to the surface of magnetic Fe₃O₄ nanoparticles. The effects of initiator dosage, monomer concentration, and reaction temperature on the characteristics of surface-modified Fe₃O₄ nanoparticles were investigated. Moreover, the Fe₃O₄-g-PAA hybrid nanoparticles were dispersed in water to form ferrofluids (FFs). The obtained FFs were characterized by UV–vis spectrophotometer, Gouy magnetic balance and laser particle-size analyzer. The testing results showed that the high-concentration FF had excellent stability, with high susceptibility and high saturation magnetization. The rheological properties of the FFs were also investigated using a rotating rheometer.     

用于双色全息存储（Fe，Cu）：LiNbO3晶体的参量优化计算

在确定Cu在LiNbO3晶体中对应于365nm和633nm的激发系数、复合系数、光伏系数的基础上，采用龙格-库塔（Runge-Kutta）数值方法理论研究了双掺杂（Fe，Cu）：LiNbO3晶体的深浅能级的掺杂组分比、氧化-还原状态对双色全息存储的记录灵敏度和动态范围的影响，并探讨了同时取得尽可能大的灵敏度和动态范围的晶体条件。结果表明，为了同时得到较大的记录灵敏度和动态范围，在实际应用中选用浅能级掺杂浓度为5．0×10^25m^-3，深能级掺杂浓度为3×10^24～3×10^25m^-3之间的弱氧化晶体是合适的。     

A First-Principles Investigation of the Structural and Magnetic Stability of Fe/GaAs(001)

The electronic properties of the interface of Fe/GaAs(001) have been investigated by using first-principles and molecular-dynamics techniques. While the ground state is ferromagnetic for all structures considered, a ferrimagnetic spin structure is found to be very close in energy (<1 meV). The observed lowering of the magnetic moments when relaxing the atomic positions is believed to be connected to this close in energy lying metamagnetic state. On the other hand, the magnetic moments of the Fe atoms at the interface are large, which can be explained by the bulk-like behavior of the density ot states of interface atoms.     

孔径型超分辨近场结构光盘的掩膜热效应分析

基于高斯聚焦激光束热效应的超分辨近场结构光盘存储（孔径型Super-RENS）中，应用光学特性导纳矩阵建立的盘片光传导模型，采用有限元分析软件FEMLAB对不同激光功率和脉宽下的Sb掩膜层的孔径形成情况进行数值仿真.结果表明，当一定脉宽的激光功率超过介质的阈值时，掩膜层将有超分辨孔径形成，且孔径大小随功率的增大而增大.理论分析与孔径型Super-RENS光盘样片在不同激光功率下进行写入的实验结果相符，说明光热效应可以较好地描述孔径型Super-RENS光盘掩膜层孔径形成的过程. 关键词： 光存储 孔径型 超分辨近场结构 光热效应     

Magnetic contribution to heat capacity and entropy of nickel ferrite (NiFe2O4)

The heat capacity of nickel ferrite was measured as a function of temperature from 50 to 1200 °C using a differential scanning calorimeter. A thermal anomaly was observed at 584.9 °C, the expected Curie temperature, T_C. The observed behavior was interpreted by recognizing the sum of three contributions: (1) lattice (vibrational), (2) a spin wave (magnetic) component and (3) a λ-transition (antiferromagnetic-paramagnetic transition) at the Curie temperature. The first was modeled using vibrational frequencies derived from an experimentally-based IR absorption spectrum, while the second was modeled using a spin wave analysis that provided a T^3/2 dependency in the low-temperature limit, but incorporated an exchange interaction between cation spins in the octahedral and tetrahedral sites at elevated temperatures, as first suggested by Grimes [15]. The λ-transition was fitted to an Inden-type model which consisted of two truncated power law series in dimensionless temperature (T/T_C). Exponential equality (m=n=7) was observed below and above T_C, indicating symmetry about the Curie temperature. Application of the methodology to existing heat capacity data for other transition metal ferrites (AFe₂O₄, A=Fe, Co) revealed nearly the same exponential equality, i.e., m=n=5.     

冷原子的双阱微磁表面囚禁

提出了两种新颖的采用载流导线的双阱微磁表面囚禁方案(即双U形与双Z形导线囚禁)。通过改变囚禁方案中直导线中的电流方向，即可将双U形导线囚禁改变为双Z形导线囚禁；如果逐渐减小直导线中的电流大小，即可将一个双阱微磁囚禁连续地合并为一个单阱微磁囚禁，反之亦然。详细计算和分析了上述两种载流导线囚禁方案的磁场及其梯度的空间分布。研究发现在导线中通以较小的电流，即可在导线表面附近产生很大的磁场梯度及其曲率。例如当电流为O．2A时，其磁场梯度和曲率可分别达到0．2T／cm和10T／cm2以上。由于双U形导线囚禁中存在磁场零点，而双Z形导线囚禁中仅存在磁场最小值，所以双U形导线囚禁仅适用于制备双样品磁光囚禁(MOT)或研究中性原子的冷碰撞，而双Z形导线囚禁除了可用于研究原子的冷碰撞之外，还可以用于制备双样品玻色-爱因斯坦凝聚(BEC)或实验研究双阱玻色-爱因斯坦凝聚的性质等。