Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1995 Vortex lattice melting in an anisotropic type II superconductor John Anton Fendrich Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Condensed Matter Physics Commons, and the Materials Science and Engineering Commons Recommended Citation Fendrich, John Anton, "Vortex lattice melting in an anisotropic type II superconductor " (1995). Retrospective Theses and Dissertations. 10899. https://lib.dr.iastate.edu/rtd/10899 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. 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Signature was redacted for privacy. For the Major Department Signature was redacted for privacy. Signature was redacted for privacy. For the Uraduate College Signature was redacted for privacy. Iowa State University Ames, Iowa 1995 Copyright (c) John Anton Fendrich, 1995. All rights reserved. DMI Number: 9531735 UMI Microform 9531735 Copyright 1995, by OMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17r United States Code. UMI 300 North Zeeb Road Ann Arbor, HI 48103 TABLE OF CONTENTS ACKNOWLEDGEMENTS ix CHAPTER 1. INTRODUCTION 1 CHAPTER 2. THEORY 6 2.1 Introduction 6 2.2 Vortex Melting 9 2.2.1 Elastic Behavior 11 2.2.2 Thermodynamics of Phase Transitions 14 2.3 Vortex Pinning 16 2.3.1 Introduction 16 2.3.2 Elementary Pinning Force of Point Defects 18 2.3.3 Summation Theories of Flux Pinning 20 2.4 Vortex Dynamics 26 2.5 Electron Irradiation 29 CHAPTERS. EXPERIMENTAL METHODS 33 3.1 YBa2Cu20y ^ 33 3.1.1 Introduction 33 3.1.2 Crystal Growth 36 3.1.3 Crystal Detwinning 45 iii 3.2 Experimental Set Up 51 3.2.1 Cryogenics 51 3.2.2 Resistivity Measurements 56 CHAPTER 4. VORTEX MELTING IN YBa2Cu307_5 61 4.1 Experimental Results 61 4.1.1 Introduction 61 4.1.2 H||c-axis Results 67 4.1.3 H||ab-plane Results 83 4.2 Discussion 88 4.3 Conclusions 96 CHAPTERS. ELECTRON IRRADIATION 98 5.1 Introduction 98 5.2 Experimental Results 99 5.2.1 Introduction 99 5.2.2 Point Defect Production 100 5.2.3 H||c-axis Results 101 5.2.4 Hl|ab-plane Results 107 5.2.5 Results from Sample Annealing 117 5.3 Discussion 127 5.4 Conclusions 142 CHAPTER 6. CONCLUSIONS 144 REFERENCES 147 iv LIST OF FIGURES Figure 2.1: Phase Diagram for High Temperature Superconductor .... 8 Figure 2.2: Percent Transmission versus Range for Electrons 32 Figure 3.1: Structure of the YBa2Cu30y_^ Unit Cell 34 Figure 3.2; Crystal Growth Phase Diagram 38 Figure 3.3: Crystal Growth Temperature Profile 41 Figure 3.4: Diamagnetic and Resistivity Measurements of Two Samples from Two Different Batches of Growth 44 Figure 3.5: Twinned YBa2Cu30y_^ Single Crystal 46 Figure 3.6: Twinned and Untwinned YBa2Cu30'j'_^ Single Crystal ... 49 Figure 3.7: Detwinning Device 50 Figure 3.8: 8 + 1.5 Tesla Cryostat 52 Figure 3.9: Top View of Cryostat 53 Figure 3.10: 8T Magnet Support 54 Figure 3.11: 8T Magnet Insert 55 Figure 3.12: Sample Holder and Electronics 58 Figure 4.1: Resistivity of Twinned Crystal for Ha H c-axis 62 Figure 4.2: Resistivity of Twinned Crystals versus Applied Field Direction 65 Figure 4.3 Resistivity of a Twinned and Untwinned Crystal in Zero field 69 Figure 4.4 Resistivity of Twinned and Untwinned Portions of Same Crystal 70 Figure 4.5 Resistivity of Untwinned Crystal for Ha 1| c-axis 71 Figure 4.6 Comparison of Melting Width for Twinned and Untwinned Crystals 73 Figure 4.7; Melting as a Function of Field in an Untwinned Crystal ... 74 Figure 4.8: Voltage-Current Characteristics of Untwinned YBa2Cu307_^ Single Crystal 76 Figure 4.9: Non-Ohmic Behavior in a YBa2Cu30y_g Single Crystal with Two Twin Boundaries 77 Figure 4.10: Hysteresis in Melting Transition 79 Figure 4.11: Resistivity at Fixed Temperature of a Twinned Crystal and an Untwinned Crystal at Different Current Densities versus Applied Magnetic Field 81 Figure 4.12: Minor Hysteresis Loops at Vortex Melting 82 Figure 4.13: Peak Effect 84 Figure 4.14: Solid state Instabilities in an Untwinned Crystal 85 Figure 4.15: p — Tiox Applied Fields Aligned with the c-axis and ab-planes 87 Figure 4.16: Hysteresis for Magnetic Field AUgned with the ab-plane ... 89 Figure 4.17: Ratio of Vortex Spacing to Vortex Radius 91 Figure 5.1: Resistivity Before and i4/ter Electron Irradiation for Ha || c-axisl03 Figure 5.2: Resistivity Before and y4/ter Electron Irradiation for Ha || c-axis 104 Figure 5.3: Reduced Resistivity Before and After Electron Irradiation for Ha 11 c-axis 106 vi Figure 5.4; V-I Curves Before and A/ter Electron Irradiation for Ha =0.5T1| c-axis 108 Figure 5.5: V-I Curves Before and After Electron Irradiation for H = 4T|| c-axis 109 Figure 5.6: V-I Curves Before and A/ter Electron Irradiation for Ha =7T|| c-axis 110 Figure 5.7: R vs T Curves Before and A/ierElectron Irradiation for Ha =0.5T|| c-axis and V-I Data Temperatures Ill Figure 5.8: R vs T Curves Before and Ayiter Electron Irradiation for Ha =4T|| c-axis and V-I Data Temperatures 112 Figure 5.9: pvsT Curves Before and i4/ter Electron Irradiation for Ha =7T|| c-axis and V-I Data Temperatures 113 Figure 5.10: Resistivity vs Temperature Before and After Electron Irradi­ ation for Ha II ab-plane 115 Figure 5.11: Reduced Resistivity Before and After Electron Irradiation for Ha II ab-plane 116 Figure 5.12: Current Dependence of the Reduced p-T Before and After Electron Irradiation for 8T|| ab-plane 118 Figure 5.13: V-I curves A/ter Electron Irradiation for 0.5 and 8T|| ab-plane 119 Figure 5.14: Temperatures where V-I curves were taken After Electron Ir­ radiation for 8 and 0.5T|| ab-plane 120 Figure 5.15: Annealing Effects on the Zero-Field Resistive Transition ... 122 Figure 5.16: After 150°C and 2"'^C 180°C anneal 123 Figure 5.17: After 150°C and 2"'^C 180°C anneal 125 Vll Figure 5.18: After 1®^ 200°C and 220°C anneal 126 Figure 5.19: Reduced Resistivity for H = 4T|| c-axis After Various Anneal­ ings 128 Figure 5.20: Resistive Hysteresis in Field for H|| c-axis After Annealing Sample 129 Figure 5.21: Reduced Resistive Transition for H|| c-axis Before Irradiation, Immediately After Irradiation, and After Annealing 130 Figure 5.22: Scaling for Vortex-Glass 132 Figure 5.23: Bardeen-Stephen Flux Flow Resistivity 134 Figure 5.24: Resistivity at Fixed Temperature Before Irradiation 136 Figure 5.25: pp vs T/Tc and Up 138 Figure 5.26: pp vs T/Tc and Up 139 Vlll LIST OF TABLES Table 3.1: A Summary of the Superconducting Transition Temperatures Tc, TVansition Widths ATc Determined from Resistivity Mea­ surements, and a Brief Description of the Crystal ! . 43 Table 5.1; Summary of Crystal Annealings i4yiter Electron Irradiation . 121 ix ACKNOWLEDGEMENTS The work in this thesis was supported by the National Science Foundation - OfRce of Science and Technology Centers under the Grant #DMR91-20000 Science and Technology Center for Superconductivity and the United States Department of Energy, Basic Energy Sciences - Materials Science under contreict #W-31-109-ENG- 38.