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首页> 外文学位 >An investigation of electrodynamic properties of high transition temperature superconducting yttrium barium(2) copper(3) oxygen(7-delta) single crystals.
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An investigation of electrodynamic properties of high transition temperature superconducting yttrium barium(2) copper(3) oxygen(7-delta) single crystals.

机译：高转变温度超导钇钡（2）铜（3）氧（7-δ）单晶的电动力学性质研究。

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Microwave induced dc voltages along the c-axis with or without a dc bias current and magnetic interference effects in YBCO single crystals have been studied. To study the microwave induced dc voltages, the sample was mounted near the end of an X-band waveguide such that the microwave H-field is in the ab-planes and the E-field parallel to the c-axis of the single crystal sample. Since the maxima of E- and H-fields of the microwaves are separated by one quarter of wavelength near the end of the waveguide, the single crystal sample can be coupled to the E- or the H-fields of the microwaves selectively by moving the adjustable end near the end of the waveguide. Microwave induced dc voltages have been studied under a variety of conditions including various sample positions, frequencies, bias current levels and media such as liquid oxygen, liquid nitrogen, oxygen gas and nitrogen gas. With a dc bias current, the effect is larger when the single crystal sample is coupled to the maximum of the microwave H-field, suggesting that the induced dc voltages are due to vortex flow. Without a dc bias current, the induced dc voltages resemble the inverse ac Josephson effect and require the presence of both the E- and H-fields of the microwave. The observed phenomena indicate the existence of multiple Josephson junctions inside a single crystal sample.;For the magnetic interference measurements, the sample was biased at a constant dc current in the c-axis direction such that a small dc voltage developed and then a dc magnetic field parallel to the ab-planes of the single crystal was applied to search for an effect. Since the change in the voltage signal is comparable to the noise level of the nanovoltmeter, a more sensitive technique was employed. In a addition to a dc magnetic field, a low-frequency magnetic field perpendicular to the dc field was applied to modulate the critical current of the sample. Using this technique, the small voltage changes as a function of dc magnetic field can be detected at modulation frequency by a lock-in amplifier. We have observed periodic voltage oscillations as a function of the applied dc magnetic field parallel the ab-planes of a
机译：研究了在YBCO单晶中有无直流偏置电流时微波沿c轴感应的dc电压和磁干扰效应。为了研究微波感应的直流电压，将样品安装在X波段波导的末端附近，以使微波H场位于a平面中，而E场平行于单晶样品的c轴。 。由于微波的E场和H场的最大值在波导末端附近被四分之一的波长隔开，因此可以通过移动单晶样本选择性地耦合到微波的E场或H场。可调端靠近波导的末端。已经在各种条件下研究了微波感应的直流电压，包括各种样品位置，频率，偏置电流水平以及诸如液氧，液氮，氧气和氮气等介质。对于直流偏置电流，当单晶样品耦合到微波H场的最大值时，影响更大，这表明感应的直流电压是由于涡流引起的。如果没有直流偏置电流，则感应的直流电压类似于交流约瑟夫逊效应，并且需要同时存在微波的电场和电场。观察到的现象表明在一个单晶样品中存在多个约瑟夫逊结。;对于磁干扰测量，样品在c轴方向上以恒定的dc电流偏置，从而产生了小的dc电压，然后产生了dc磁施加平行于单晶的ab平面的场以寻找效果。由于电压信号的变化可与纳伏表的噪声水平相比，因此采用了更为灵敏的技术。除直流磁场外，还施加垂直于直流磁场的低频磁场来调制样品的临界电流。使用这种技术，锁相放大器可以在调制频率下检测到微小的电压变化，该电压变化是直流磁场的函数。我们已经观察到周期性电压振荡是平行于a的ab平面的施加的dc磁场的函数

著录项

  • 作者

    Ling, Dah-Chin.;

  • 作者单位

    Wayne State University.;

  • 授予单位 Wayne State University.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 1995
  • 页码 88 p.
  • 总页数 88
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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