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有读书笔记Broadband electrodynamic measurement techniques for multiferroics with applications to BiFeO3 crystals

热1 handsomeland 添加于 2010-6-23 14:16 | 5403 次阅读 | 0 个评论

  •  作 者

    J Lu

  •  摘 要

    Multiferroics mean those crystals which simultaneously possess memorizable spontaneous charge orderring and memorizable spontaneous spin orderring. Multiferroic materials usually strongly interact with external electrical field, magnetic field or electromagnetic waves et al., so that they may emerge new interesting physical phenomena and promise a bright future for applications. Therefore, undoubtably multiferroics has become one of the hottest topics in the condensed matter physics community. On the other hand, during the overwhelming development of multiferroics, one frequently reads various experimental results which are unfortunately not consistent to each other. Most multiferroic experimental results, taking ferroelectric hysteresis, magnetic hysteresis, dielectric spectrum, permeability spectrum, magnetoelectric spectrum, optical properties et al. for example, have been coming from electrodynamic measurement in particular temperature and frequency windows. To get significant multiferroic experimental results, convincing electrodynamic measurement methods need to be established, as well as using high quality samples. This work was also motivated to help understanding new multiferroic experimental results. This work has described detailed methods of quality multiferroic measurement for DC experiments and AC measurement techniques from 1 mHz to 1k THz with 18 decades, as well as evaluation methods. This work also invesigates phase equilibra knowledge of BiFeO3 using high purity starting materials (>99.999 wt.%) and improved Bi2O3-Fe2O3 phase diagram. Based on measurement techniques and high-quility BiFeO3 crystals, this work has found some new results for BiFeO3 mainly summarized as follows: 1) The antiferromagnetic phase transition is close to 635 K. No additional magnetic transitions such as spin reorientation or glass behaviours have been found between 2 and 800 K. 2) The intrinsic room-temperature dielectric constant is about 54, along pseudo-cubic c axis and with measurement frequency around 120 GHz.

  •  详细资料

    • 文献种类:学位论文
    • 期卷页: 2010年
    • 日期: 2010-6-23

  •  标 签

    BiFeO3-stability  dielectrics  BDS  Magnetoelectric  multiferroic  broadband  BiFeO3  BiFeO3-VIP  BiFeO3 thermal stability  heat capacity  specific heat  THz detection  BiFeO3 dielectric  FE hysteresis  optical properties  BiFeO3 conductivity  BiFeO3 magnons  BiFeO3 review  crystal growth  BiFeO3 phonons  BiFeO3 single crystal  BiFeO3 structure  BiFeO3 phase diagram  BiFeO3 optical  BiFeO3 structures  BiFeO3 magnetism  BiFeO3 china  BiFeO3 stability  BiFeO3 phase transitions 

  •  handsomeland 的文献笔记  订阅

    Draft of my thesis in english has been written. To make the thesis more readable, at the moment the maintext is under improvement by my supervisors in Univ. Augsburg, Germany. As soon as my supervisors nod for publishing it online, i will put the fulltext here.

     

    When you are familiar with chinese, it is strongly recommended you read the chinese version http://www.xinkexue.com/bib-ref-refid-5526.html . However, if you have problem with chinese and you cannot wait for some while, please not hesitate to tell me (my email: jlu at mail.ipc.ac.cn). i would like to send the fulltext to your mailbox, in the condition that you promise NOT propagating my thesis to any other people before my thesis is formally published.

     

    Here are the Contents:

    Aknowledgement .....1
    Abstract ...3
    1 Introduction..............................- 1 -
    2 Background .............- 3 -
    2.1 Multiferroics: development and typical types.........- 9 -
    2.2 Structures and properties of BiFeO3 .........- 12 -
    2.2.1 Structural features of BiFeO3 .....- 13 -
    2.2.2 Physical properties of BiFeO3 .....- 18 -
    2.2.3 Issues about physical properties of BiFeO3 ..- 19 -
    3 Investigation of BFO crystals growth ......- 21 -
    3.1 Thermodynamic properties of BFO ......- 21 -
    3.2 Crystal growth of BFO......- 27 -
    3.3 Selection and pretreatment of BFO crystals.......- 31 -
    4 Broadband electrodynamic measurement techniques .......- 35 -
    4.1 Measurement of steady properties ........- 36 -
    4.1.1 Measurement of dc resistance ......- 36 -
    4.1.2 Direct measurement of XE effect.......- 38 -
    4.1.3 Measurement of dc magnetic moment ......- 41 -
    4.2 Low-frequency measurement......- 44 -
    4.2.1 Measurement of ac impedance/dielectric spectrum .....- 44 -
    4.2.2 Equivalent circuit techniques for impedance/dielectric analysis ...- 48 -
    4.2.3 Cautions in analysis of ac impedance/dielectric data...- 52 -
    4.2.4 Ferroelectric hysteresis measurement .....- 55 -
    4.2.5 Magnetic hysteresis and ac susceptibility measurement....- 59 -
    4.2.6 Lock-in techniques and precision magnetoelectric measurement....- 60 -
    4.2.7 “abnormal”resonances at low frequencies .....- 66 -
    4.3 Microwave measurement .......- 66 -
    4.3.1 Transmission line, waveguide and cavity......- 67 -
    4.3.2 Coaxial broadband measurement in microwave region.....- 69 -
    4.3.3 Skin effect .....- 72 -
    4.3.4 magnetic and “abnormal” resonance effect in microwave range.....- 74 -
    4.4 THz measurement ......- 76 -
    4.5 Broadband optical measurement......- 78 -
    4.6 Auxiliary measurement techniques .........- 80 -
    4.6.1 Cryostat and furnace for measurement .......- 81 -
    4.6.2 Measurement of specific heat....- 82 -
    4.7 Summary of broadband measurement techniques......... - 83 -
    5 Broadband electrodynamic properties of BFO crystals........ - 85 -
    5.1 Magnetic measurement......... - 85 -
    5.2 Dielectric measurement ...... - 88 -
    5.2.1 Estimation of the true dielectric constant .... - 88 -
    5.2.2 Analysis of conductivity ..... - 93 -
    5.2.3 Low-temperature ferroelectric hysteresis measurement.... - 95 -
    5.3 Specific heat capacity measurement..... - 97 -
    5.4 Other results....... - 99 -
    5.4.1 High-temperature dielectric measurement of BFO crystals .... - 99 -
    5.4.2 Measurement results of BFO polycrystals...... - 102 -
    5.5 Analysis of BFO broadband measurement results... - 105 -
    6 Summary and prospect ....... - 107 -
    Bibliography ...... - 109 -
    Curriculum Vitae of the author....... - 130 -

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