Influences of Bi2O3/V2O5 Additives on the Microstructure and Magnetic Properties of Lithium Ferrite

Lithium ferrite materials with different concentrations of Bi2O3 and V2O5 additives are prepared by the conventional ceramic technique. The x-ray diffraction analysis proves that the additives do not affect the final crystal phase of the lithium ferrite in our testing range. Both Bi2O3 and V2O5 additives could promote densification and lower sintering temperature of the lithium ferrite. The average grain size first increases, and then gradually decreases with the Bi2O3 content. The maximal grain size appears with 0.25 wt% Bi2O3. The average grain size first increases, and then is kept almost unchanged with the V2O5 content. The maximal average grain size of the samples with V2O5 additive is much smaller than that of the samples with Bi2O3 additive. Furthermore, the V2O5 additive more easily enters the crystal lattice of the lithium ferrite than the Bi2O3 additive. These characteristics evidently affect the magnetic properties, such as saturation flux density, ratio of remanence Br to saturation flux density Bs, and coercive force of the lithium ferrite. The mechanisms involved are discussed.     

Perpendicularly oriented barium ferrite thin films with low microwave loss,prepared by pulsed laser deposition

Barium ferrite(Ba M) thin films are deposited on platinum coated silicon wafers by pulsed laser deposition(PLD).The effects of deposition substrate temperature on the microstructure,magnetic and microwave properties of Ba M thin films are investigated in detail.It is found that microstructure,magnetic and microwave properties of Ba M thin film are very sensitive to deposition substrate temperature,and excellent Ba M thin film is obtained when deposition temperature is 910℃ and oxygen pressure is 300 m Torr(1 Torr = 1.3332×10~2Pa).X-ray diffraction patterns and atomic force microscopy images show that the best thin film has perpendicular orientation and hexagonal morphology,and the crystallographic alignment degree can be calculated to be 0.94.Hysteresis loops reveal that the squareness ratio(M_r/M_s) is as high as 0.93,the saturated magnetization is 4004 Gs(1 Gs = 10~4T),and the anisotropy field is 16.5 kOe(1 Oe = 79.5775 A·m~(-1)).Ferromagnetic resonance measurements reveal that the gyromagnetic ratio is 2.8 GHz/kOe,and the ferromagnetic resonance linewith is108 Oe at 50 GHz,which means that this thin film has low microwave loss.These properties make the Ba M thin films have potential applications in microwave devices.     

晶格失配应力对单晶(BiTm)_3(GaFe)_5O_(12)膜磁畴结构的影响

利用液相外延工艺在钆镓石榴石衬底上制得了单晶(BiTm)_3(GaFe)_5O_(12)膜,研究了晶格失配应力对其磁畴结构的影响.研究发现,生长速率越快,膜的晶格常数越大;晶格失配应力可以在一定范围内调整膜的垂直各向异性;随着晶格失配应力由较大张应力逐渐转变为较大压应力,磁畴形状先由磁泡畴转变成迷宫畴,然后转变为过渡态部分弯曲的条状畴,最终转变为整齐排列的条状畴;失配应力同时对畴宽也有影响,膜受到的失配应力越大,畴宽越大.这一实验研究对基于控制晶格失配应力来调控单晶膜的各向异性和磁畴结构有指导意义.     

Liquid phase epitaxy magnetic garnet films and their applications

Liquid phase epitaxy(LPE) is a mature technology. Early experiments on single magnetic crystal films fabricated by LPE were focused mainly on thick films for microwave and magneto–optical devices. The LPE is an excellent way to make a thick film, low damping magnetic garnet film and high-quality magneto–optical material. Today, the principal challenge in the applied material is to create sub-micrometer devices by using modern photolithography technique. Until now the magnetic garnet films fabricated by LPE still show the best quality even on a nanoscale(about 100 nm), which was considered to be impossible for LPE method.     

Additional Y3+ Doping Effect on Ferromagnetism of Ce0.97Co0.03O2-δ Compounds

Y^3＋ doping effect on magnetic properties of Ce0.97Co0.03O2-δ are examined. Vibrating sample magnetometer （VSM） measurements indicate that Ce0.97Co0.03O2-δ is ferromagnetic at room temperature. The saturated magnetization Ms is altered by additional Y^3＋ doping, i.e., with the increase of the amount of Y^3＋ doping concentration in Ce0.97-yYyCo0.03O2-δ（y = 0.01, 0.05 and 0.10）, Ms increases persistently, Raman spectra measurements indicate that additional oxygen vacancies are introduced with the amount of Y^3＋ doping content. The results can be well elucidated by the F-centre exchange coupling （FCE） mechanism proposed recently, thus they are important for understanding the ferromagnetism origination in transitional metal-doped insulating oxides.     

低温共烧陶瓷埋置电感和电容的研究

讨论了低温共烧陶瓷(LTCC)埋置电感、电容的几何结构,并进行仿真,分析了结构变化对电感性能的影响,并进行实验制作,通过测试样品以验证仿真结果。仿真结果中找到的规律有效的节省了器件设计的时间,为等效模型的提取和元件库的建立奠定了一定的基础。     

信息存储材料的现状与未来

信息存储材料的研究与开发直接影响着整个信息技术的发展进程。本文从磁光存储材料，磁存储材料、光存储材料和纳米存储材料四个方面评述了现代信息存储材料应用于电子领域中的现状，并就其前景及今后研究方向进行了讨论。     

铱掺杂溴化银微晶的瞬态光电导研究

研究在77K时，铱掺杂溴化银微晶瞬态光电导（TPC）的信号强度和衰减时间与铱掺杂浓度间的关系。在溴化银微晶的制备过程中，IrCl6^3-作为掺杂剂加入，使溴化银微晶中的部分银离子所占据的晶格位被铱离子取代，在溴化银晶体中同时引入新的电子陷阱与空穴陷阱，增强了内部的电子空穴复合，使TPC的信号强度随铱离子掺杂浓度的增大而减小。     

用混合材料镀制激光反射镜

用（Ｔａ２Ｏ５＋ＺｒＯ２）和ＳｉＯ２成功地镀制出两个波段的激光反射镜，使激光破坏阈值提高５％－１５％，膜层吸收小，机械强度增加，理论计算和测量混合成分含量表明，膜成分与配比成分存在６％－１３％的偏差。     

诱导透射干涉滤光片的设计及其镀制工艺

介绍可见光区诱导透射滤光片(简称ITF)的设计和镀制方法,给出透射率随膜层变化的部分理论曲线和实验曲线,讨论金属Ag层厚度和间隔层的变化对ITF透射率和截止宽度的影响。应用直透法监控层厚的工艺,第一间隔层最终控制在透射率高于起始点0.5—0.7％左右时较佳。镀Ag时厚度最终控制在其透射率起始下降到最低点附近较为适宜。