2007 Annual Report Vol.35 - 中研院物理研究所- Academia Sinica

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field up to 20 T and pressure up to 20 kbars in a dilution refrigerator. We also have setups for the preparation of nanoparticles, thin film and single crystals. Some past research accomplishments are summarized in the following: • We have observed several interesting quantum-size effects on the magnetisim and superconductivity in nanomaterials of heavy fermion systems. • We have developed the new methods for the production of high quality magnetic/superconducting nanoparticles and thin films • We have developed a new wide-range low temperature sensor for calorimeter application using transition metal oxides. • We have observed the coexistence of magnetic order and superconductivity in Ru-based double perovskite oxides. Major research achievements: 1. A world-class high-pressure thermal-relaxation microcalorimeter We have developed a high-pressure thermal-relaxation microcalorimeter. It integrates our earlier developed thermal-relaxation microcalorimeter with a pair of diamond anvils, covering the temperature range of 0.3-30 K and applied pressure up to 10 Kbar. Major difficulties requiring innovative solutions to thermally isolate the sample and diamond anvils from the environment. The system has now been tested and used for the pressure dependence of heat capacity for heavy fermion nanoparticles. 2. Measuring system for electrical and thermal transport properties of a single nanowire We have devoted to the study of thermoelectric nanomaterials for many years. In order to obtain the intrinsic properties of Seebeck coefficient, electrical conductivity and thermal conductivity of a nanodevice, a measuring system has been developed and successfully applied to single nanowires prepared by anodic-aluminum-oxide template and the lithography technique. A single nanowire is suspended in vacuum with its two ends in contact with the substrate for thermal insulation. By applying the 3ωmethod, the intrinsic t hermal and transport properties of the nanowire can be obtained. The results on a single Ni nanowire (Φ= 200 nm and L= 10 um) have been reported (Applied Physics Lett, 91, 251907, <strong>2007</strong>). 3. Initiating an innovative research field -- novel physical properties of heavy fermion nanoparticles 18
3-1. Kondo enhancement and antiferromagnetic order suppression in nanoparticles It is known that magnetic ordering and Kondo behavior coexist in three (Ce,Al)-based compounds, CeAl 2 , Ce 3 Al, and Ce 3 Al 11 . As the particle size is reduced to nanoscale, the specific heat anomaly associated with the magnetic ordering diminishes. Although the Kondo temperature also decreases, the entropy associated with Kondo anomaly exhibits a large increase. This results in an enhancement of the Kondo behavior as well as an increased coefficient γ of the linear term in specific heat. For example, in 8 nm-CeAl 2 , magnetic ordering completely disappears and the Kondo temperature decreases to 0.65 K (from 5 K for bulk CeAl 2 ). Meanwhile, the extrapolated γ reaches 9000 mJ/mol Ce K 2 as the temperature approaches zero. This value falls in the highest range ever reported for heavy fermion compounds and was reported to PRL. It is worthy to mention that we started the research work and performed most of experiments in our lab, resulting in a successful publication. 3-2. Different size effect between ferromagnetic and antiferromagnetic ordering Bulk Ce 3 Al 11 undergoes a ferromagnetic ordering at T C =6.2 K, followed by an antiferromagnetic ordering at T N =3.2 K. In Ce 3 Al 11 nanoparticles, the ferromagnetic transition remains at T C =6.2 K, but no antiferromagnetic transition is visible down to 1.8 K. Meanwhile, a slightly smaller Curie constant of nanoparticles as compared to that of the bulk indicates a certain degree of demagnetization of Ce ions with size reduction(Phys. Rev. Lett. 84, 4990, 2000). 3-3. Lattice Disorder and Size-Induced Kondo Behavior in CeAl 2 and CePt 2+x When the size of CeAl 2 and CePt 2+x particles is reduced to the nanometer scale, antiferromagnetism is suppressed and Kondo behavior predominates, with the Kondo temperature T K either decreasing (CeAl 2 ) or increasing (CePt 2+x ) relative to the bulk. Extended x-ray absorption fine structure (EXAFS) measurements show that these nanoparticles are significantly distorted. While such distortions should strongly affect magnetic and electronic properties, we find that they cannot explain the observed changes in T K . Other size-induced changes to the electronic structure must, therefore, play a significant role. The results were published in (Phys. Rev. Lett. 97, 097204, 2006) 3-4. The evolution of Kondo interactions and magnetic correlation with size variation and Core (magnetic)- shell (nonmagnetic) model in CePt 2 The evolution of the Kondo effect and antiferromagnetic correlations with size reduction in CePt 2 nanoparticles (3.1-26 nm) is studied by analysis of the temperature-dependent specific heat and magnetic susceptibility. The antiferromagnetic correlations diminish with size reduction. The Kondo effect predominates at small particle size with trivalent, small Kondo temperature magnetic regions coexisting with strongly mixed valent, large T K nonmagnetic regions. 19
Page 1 and 2: 中央研究院物理研究
Page 3 and 4: 中央研究院物理研究
Page 5 and 6: I Members of the Institute
Page 7 and 8: 胡進錕研究員 / 統計
Page 9 and 10: 鄭天佐特聘講座 / 表
Page 11 and 12: 郭鴻曦助研究員 / 單
Page 13 and 14: Adjunct Faculty 姚永德 Yeong-D
Page 15 and 16: Yu-Kuo Hsiao ( 蕭佑國 ) Li-Lin
Page 17 and 18: II Review of Research Projects
Page 19 and 20: The Institute of Physics Logo The l
Page 21 and 22: • We have we demonstrate an astig
Page 23: Homemade atomic force microscope us
Page 27 and 28: 4 2 (a) bulk C Kondo (0.6 mol Ce, T
Page 29: III. Spintronics, magnetic nanostru
Page 33 and 34: 1 μm 1 μm Gold nano-particle patt
Page 35 and 36: (a) 15C ssDNA 15A ssDNA (b) 60 600
Page 37 and 38: Chii-Dong Chen Research Fellow Tel
Page 39 and 40: Kuo,Hong-Shi Assistant Research Fel
Page 41 and 42: Intermediate and High Energy Physic
Page 43 and 44: III. Particle Physics Experimental
Page 45 and 46: 3. The shielding and control room a
Page 47 and 48: Hai-Yang Cheng Research Fellow Tel
Page 49 and 50: Research Interest: Theoretical Nucl
Page 51 and 52: III. Statistical and Computational
Page 53 and 54: 靠將膠體小球與高分
Page 55 and 56: Yeng-Long Chen Assistant Research F
Page 57 and 58: III List of Ongoing Research Projec
Page 59 and 60: 主持人計劃名稱執行
Page 65 and 66: IV Publication List of 2007
Page 67 and 68: Chang, C. S.( 張嘉升 ) 1. S. M
Page 69 and 70: 9. S. U. Jen, T. C. Wu, C. M. Wong,
Page 71 and 72: 3. H.Y. Cheng, C.K. Chua and K.C. Y
Page 73 and 74: 7. E. F. Aziz, S. Eisebitt, F. de G
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12. “First Measurement of the W B
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through the reaction 0703 (2007) 01
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in the presence of counterions, Phy
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29. C.-K. Hu. Quantum and lattice m
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2. J. H. Liao*, T. B. Wu, S. T. Ho,
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4. L. J. Chang, A. L. Chen, K. W. C
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Leung K.-t. ( 梁鈞泰 ) 1. Floc
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Lin, Shin-Ted( 林興德 ) 1. " L
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2. ATLAS Commissioning, Preparation
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13. The CDF Collaboration, Precisio
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Decays” i. T. Aaltonen et al., Th
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20. “Cross Section Constrained To
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2007. 37. “Search for Exclusive g
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A. Abulencia et al., The CDF Collab
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3. Rao SM, Wu MK , Wang KJ, Yen NY
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V Academic Activities
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會議名稱會議期間舉
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Institute Sponsored Meetings 本
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演講題目演講者所屬
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Visiting Scholars 中央研究
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訪問學人所屬機構訪
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訪問學人所屬機構訪
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2007 Annual Report Vol.35 - 中研院物理研究所- Academia Sinica

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