高压增氧T′相R_2CuO_(4+δ)(R=Nd～Tm)低温磁性研究

T′相R2CuO4稀土铜氧化合物由于尺度效应而产生弱铁磁性行为已经被人们关注,报导了通过高温高氧压(6GPa,1000℃)合成稀土T′相R2CuO4(R=Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er和Tm)化合物的结构和磁学性能。磁化率曲线显示,在低温下所有的高压增氧R2CuO4样品都出现新的低温弱铁磁性反常行为,转变温度在28K附近。新的低温弱铁磁性行为是由于CuO2面上微量氧空穴的掺入,使处于反铁磁有序CuO2面形成局域化的铁磁性团簇造成。实验证明新发现的低温弱铁磁性行为与尺度效应产生弱铁磁性行为属于完全不同的物理机制。结果还预示T′相R2CuO4稀土铜氧化合物很难通过空穴掺杂而实现超导。     

电工实践教学改革与实践

电工实践教学是培养大学生电类工程能力的重要环节，本文介绍我们以培养人才为中心在电工实习基地建设；实践教学内容，方法和手段等方面进行的改革与实践。     

网络处理器uPD98501

本文介绍了NEC公司新推出的网络处理器uPD98501,及其在ADSL中的应用。     

HA918系列电话机通话电路分析 上

ＨＡ９１８系列电话机通话电路分析（上）熊瑞香ＨＡ９１８系列电话机包括ＨＡ９１８Ｐ型、ＨＡ９１８Ｐ／Ｔ型和ＨＡ９１８Ｐ／ＴＬ型电话机。这些电话机的通话电路均采用ＴＥＡ１０６２型通话专用集成电路。图１是该集成电路的组成框图。图２示出它的各引出线各称。各端...     

电子通道技术在YBa2Cu3O7外延超导薄膜研究中的应用

本研究采用电子通道技术（ＥＣＰ）对单晶和双晶外延生长的ＹＢａ＿２Ｃｕ＿３Ｏ＿７（ＹＢＣＯ）超导薄膜的结构、取向和表面完好性作检测，并证实对衬底的预处理可改善外延超导薄膜的质量；还对ＹＢＣＯ／ＣｅＯ＿２／ＭｇＯ／ＳｒＴｉＯ３的双外延薄膜作研究。     

Investigation of External Optical Feedback Resistance of IC—DFB and GC—DFB Lasers Using a Very Simple Experimental set—up

We study the external optical feedback resistance of both index-coupled(IC) and gain-coupled distributed feed-back(DFB) lasers using a very simple experimental set-up.Though IC-DFB lasers with large coupling coefficients are found to be less sensitive to external reflection,they suffer from mode instability at high injection level.On the other hand ,the introduction of gain-coupling mechanism can significantly improve both the immunity of external optical feedback and the single mode yield of the device.     

Design and Fabrication of 1.06 μm Resonant-Cavity Enhanced Reflective Modulator with GaInAs/GaAs Quantum Wells

A resonant-cavity enhanced reflective optical modulator is designed and fabricated, with three groups of three highly strained InGaAs/GaAs quantum wells in the cavity, for low voltage and high contrast ratio operation. The quantum wells are positioned in antinodes of the optical standing wave. The modulator is grown in a single growth step in an molecular beam epitaxy system, using GaAs/AlAs distributed Bragg reflectors as both the top and bottom mirrors. Results show that the reflection device has a modulation extinction of 3 dB at -4.5 V bias.