c轴垂直取向FePt薄膜的磁和磁光性能研究

采用直流磁控溅射的方法在氧化镁(100)单晶基板上生长了一系列c轴垂直取向的FePt薄膜,通过改变沉积时的基板温度,薄膜从Fe,Pt原子无序排列的面心立方结构逐渐变化到有序排列的L10相面心四方结构.在此基础上,系统研究了FePt薄膜的化学有序度对磁和磁光性能的影响.随着有序度的增加,FePt薄膜的磁晶各向异性能,以及沿垂直方向的矫顽力、剩磁比均增加,在基板温度高于530℃时制备的薄膜中的磁晶各向异性能超过1J/cm3.同时,还观察到有序FePt合金薄膜的磁光克尔光谱(克尔转角的大小和极值所对应的跃迁光子能量)随化学有序度的显著变化.     

电化学沉积高c轴取向ZnO薄膜及其光学性能分析

采用阴极还原方法，在透明导电玻璃(ITO)上制备了高c轴择优取向的ZnO薄膜.通过X射线衍射、扫描电子显微镜等表征技术，研究了沉积电流对ZnO薄膜的结构、应力状态及表面形貌的影响；利用光致荧光光谱及透射光谱等分析方法，探讨了沉积电流变化对ZnO薄膜的光学性能的影响.研究结果显示：各沉积电流下均可制得高c轴取向的ZnO薄膜；薄膜表面形貌受电流的影响较大；从透射谱可以看出，薄膜在可见光波段有较高透射率，且薄膜厚度随沉积电流的增大而增大.光致荧光测量表明，电化学沉积的ZnO薄膜具有明显的带隙展宽.而且，随着沉积电流的增加，带隙发光强度逐渐减弱，缺陷发光逐渐增强.     

用表面磁光克尔效应实验系统测量铁磁性薄膜的磁滞回线

用自制的表面磁光克尔效应实验系统开发了研究性近代物理实验,测出铁磁性薄膜的磁滞回线,并求得克尔旋转角和克尔椭偏率.     

GdFeCo/TbFeCo磁超分辨磁光记录薄膜研究

用磁控溅射法制备了GdFeCo/TbFeCo交换耦合两层薄膜,利用不同温度的克尔磁滞回线和VSM磁滞回线研究了读出层(GdFeCo)变温磁化方向变化过程.结果表明,随温度升高读出层从平面磁化转变为垂直磁化,交换耦合两层薄膜具有中心孔探测磁超分辨的基本性能.转变过程主要受饱和磁化强度（M_s）的影响,在GdFeCo的补偿温度附近,读出层的磁化强度较小,退磁场能也较小,在交换耦合的作用下,使读出层(GdFeCo)的磁化方向发生转变.磁化方向的转变在75℃~125℃的温度范围内变化较快.     

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。     

Bi置换DyIG溅射薄膜的磁光性能与干涉效应的研究

本文报道用高频溅射法在玻璃衬底上制备的Bi置换DylG薄膜具有高的矫顽力和矩形比。在500nm波长附近,法拉第旋转角达7.5°/μm。经热磁记录的磁畴稳定。并发现薄膜表面蒸镀不同金属时,随不同波长和磁光层厚度干涉效应有较大差异。利用此特性可对石榴石记录盘片进行最佳性能设计。 关键词：     

用表面磁光克尔原理测量薄膜材料的磁性参数

以表面磁光克尔原理为机理,测量薄膜材料的磁性参数,实验上求得了饱和状态下坡莫合金的克尔偏转角,并测出了其磁滞回线.     

室温生长MgO底层诱导(001)取向FePt薄膜的有序化过程对FePt成分的依赖

室温下通过磁控溅射在表面热氧化的Si基片上生长了MgO/Fe_xPt_100-x双层膜和Fe_xPt_100-x单层膜系列样品，Fe_xPt_100-x的原子成分x=48—68.研究了热处理前后不同成分FePt薄膜的晶体结构和磁性的变化，尤其是MgO底层的引入对FePt的晶体结构和磁性的影响 关键词： FePt(001)薄膜 0相')" href="#">L1₀相     

磁光克尔和法拉第效应的完整测量

简单叙述了克尔效应和法拉第效应的原理，并从光谱学研究的角度，对克尔和法拉第旋转角和椭偏率完整磁光参数的若干种实验测量作了介绍和讨论；讨论了一种可供实用的傅里叶磁光谱分析法，可以用较少的并且是无色散的光学元件，通过旋转检偏器，对出射光强随检偏角变化的关系，作傅里叶变换，就可直接可见光区求得完整的克尔和法拉第磁光参数，同时还给出了具体的实例和测量研究的结果。     

基于SSCVD方法的a-b轴取向ZnO薄膜制备

以Zn₄(OH)₂(O₂CCH₃)₆·2H₂O为单一固相有机源,采用单源化学气相沉积法(Single sour cechem icalvapor deposition,SSCVD)在Si(100)衬底上制备ZnO薄膜,用X射线衍射(XRD)、原子力显微镜(AFM)分析ZnO薄膜样品的晶体结构和微观形貌,并用X射线光电子能谱(XPS)对薄膜的锌氧化学计量比进行了分析。研究结果表明:在非平衡条件下所得到的ZnO薄膜沿a-b轴取向生长,基片温度对ZnO薄膜生长过程影响较大,随着基片温度的升高,薄膜呈现c轴生长趋势;晶粒成柱状、尺寸均匀、膜层结构致密;薄膜样品中n_Zn:n_O=0.985。     

Magnetic anisotropy axis reorientation at ultrathin FePt films

Ultrathin FePt films (thickness between 1 nm and 5 nm) were studied for non‐volatile memories applications. The films were magnetron sputtered on monocrystalline MgO?001? substrates at 500 °C. The films are polycrystalline, except the 1 nm thick film which is not continuous. It is shown that films with thickness higher than 2.7 nm have L1₀ structure and perpendicular magnetic anisotropy, while a transition to in‐plane anisotropy occurs for thinner films. The out‐of‐plane coercivity drops from 16 kOe at the thicker film to 0.5 kOe at the thinner one.

Hysteresis cycles of FePt films as a function of film thickness.     

Very high coercivities of top-layer diffusion Au/FePt thin films

The Au/FePt samples were prepared by depositing a gold cap layer at room temperature onto a fully ordered FePt layer, followed by an annealing at 800 °C for the purpose of interlayer diffusion. After the deposition of the gold layer and the high-temperature annealing, the gold atoms do not dissolve into the FePt Ll₀ lattice. Compared with the continuous FePt film, the TEM photos of the bilayer Au(60 nm)/FePt(60 nm) show a granular structure with FePt particles embedded in Au matrix. The coercivity of Au(60 nm)/FePt(60 nm) sample is 23.5 kOe, which is 85% larger than that of the FePt film without Au top layer. The enhancement in coercivity can be attributed to the formation of isolated structure of FePt ordered phase.     

Magnetic and magneto-optical properties of Co-P films prepared by chemical deposition

Features in the formation of chemically deposited polycrystalline Co-P films with thicknesses of a few nanometers are established by analyzing film surface morphology and variation in the film magnetization. It is shown that in the thickness range below 30 nm the polar Kerr effect value θ_K changes nonmonotonically and depends on a wavelength of the incident light. For the films thicker than 30 nm, this value depends weakly on both the thickness and the wavelength. These features in the θ_K behavior are attributed to the Faraday effect, which is revealed at small thicknesses upon light reflection from the lower surface of a magnetic layer. It is found that the Faraday effect in the Co-P films exceeds that in the Co films by a factor of more than two. This effect is assumed to be caused by the presence of a Pd underlayer in the samples under study.     

Rare-earth-mediated magnetism and magneto-optical Kerr effects in nanocrystalline CoFeMn0.9RE0.1O4 thin films

A series of rare-earth (RE)-doped nanocrystalline CoFeMn_0.9RE_0.1O₄ thin films were prepared on monocrystalline silicon substrate by a sol–gel process, and the influences of the various RE³⁺ ions on the microstructure, magnetism and polar magneto-optical Kerr effects of the as-deposited films were examined. The results revealed that both of the magnetism and Kerr effect of CoFeMn_0.9RE_0.1O₄ films could be mediated by doping with various RE³⁺ ions. The trend of both M_S and H_C of CoFeMn_0.9RE_0.1O₄ films is similar to that of Bohr magneton across the series of rare-earth ions. The position of Kerr rotation peaks was red-shifted and their intensities increased, especially when doping with La³⁺, Tb³⁺, Y³⁺ or Yb³⁺ and so on. The enhanced MOKEs in CoFeMn_0.9RE_0.1O₄ nanocrystalline thin films might promise their applications for magneto-optical recording in the future.     

Amorphous Ni-Al underlayer-accelerated L10 ordering transition of FePt thin films

In the present study, we succeeded in accelerating the L1₀ ordering transition of FePt thin films by employing amorphous Ni-Al as underlayers. The coercivity H_c = 5 kOe and ordering parameter S = 0.67 of FePt thin films deposited on a Ni-Al underlayer with a thickness of ∼5 nm after 380 °C annealing for 30 min are significantly higher than those H_c = 0.4 kOe and S = 0.35 of the films without the Ni-Al underlayer. The L1₀ ordering process of and the coercivity of FePt thin films can be significantly tuned by varying the thickness of the Ni-Al underlayer.     

Composition influence on the microstructures and magnetic properties of FePt thin films

The Fex Pt 100x (10nm) (x=31-51) thin films are fabricated on Si (100) substrates by using magnetron sputtering. The highly ordered L1 0 FePt phase is obtained after post-annealing at 700℃in Fe 47 Pt 53 thin film. The sample shows good perpendicular anisotropy with a square loop and a linear loop in the out-of-plane and the in-plane direction, respectively. The variations of the magnetic domains are investigated in the films when the content value of Fe changes from 31% to 51%.     

Structure and magnetic properties of 300-nm-thick FePt films with Hf underlayer

Structure, microstructure, magnetic properties of 300-nm-thick FePt films with 10-nm-thick Hf underlayer have been studied. The experimental results showed that the very thin Hf underlayer could promote the ordering at reduced temperatures by facilitating the nucleation of the order phase, leading to refined grain size and magnetic domain size. Therefore, the permanent magnetic properties of FePt films were enhanced. (BH)_max and H_c of FePt films were greatly enhanced from 5.0–21.0 MGOe and 1.4–11.0 kOe for single layer to 10.2–23.6 MGOe and 4.5–13.2 kOe for Hf-underlayered films annealed in T_a region of 400–600 °C, respectively. Nevertheless, the severe interdiffusion between the Hf and FePt layers at T_a=800 °C resulted in the decreased S, coarsened surface morphology, grain and magnetic domain sizes, and therefore the slightly decreased (BH)_max to 18.0 MGOe.     

Effect of Cr100−xTix (x = 0-19 at.%) alloy underlayers on the high coercivity of FePt thin film below the substrate temperature of 250 °C

The effect of Cr_100−xTi_x underlayer on orderd-L1₀ FePt films was investigated. A low-temperature ordering of FePt films could be attained through changing the Ti content of Cr_100−xTi_x underlayer. The ordering temperature of the 30 nm FePt film grown on 20 nm Cr₉₀Ti₁₀ underlayer was reduced to 250 °C which is practical manufacture process temperature. An in-plane coercivity was very high to 6000 Oe and a ratio of remnant magnetization (M_r) to saturation magnetization (M_s) was as large as 0.85. This result indicates that the coercivity obtained at 250 °C by the effect of CrTi underlayer is significantly higher than those obtained at 250-275 °C by the effect of underlayers in other conventional studies. The prominent improvement of the magnetic properties of ordered FePt thin films at low temperature of 250 °C could be understood with considering the strain-induced ordering phase transformation associated with lattice mismatch between Cr underlayer and FePt magnetic layer due to an addition of Ti content.     

Magnetic and magneto-optical properties of FeRh thin films

The magnetic and magneto-optical properties of FeRh thin films epitaxially deposited onto MgO(1 0 0) substrates by RF sputter-deposition system have been investigated in conjunction with the structure. An intriguing virgin effect has been found in the M–T curves of the as-deposited FeRh thin films, which is presumably interpreted in term of a change in structural phase when heating. Also, a (negative) maximum peak of Kerr rotation at around 3.8 eV has been observed when FeRh thin films are in ferromagnetic state. The polar Kerr rotation angle is found to increase at temperatures above 100 °C, which corresponds to the antiferromagnet (AF)–ferromagnet (FM) transition of FeRh thin films.