Clemson University TigerPrints All Dissertations Dissertations 12-2008 SYNTHESIS, STRUCTURE AND MAGNETIC PROPERTIES OF OXY-ANION BASED MAGNETIC SOLIDS CONTAINING TRANSITION METAL OXIDE NANOSTRUCTURES Kulugammana gedera Ranmohotti Clemson University, [email protected] Follow this and additional works at: https://tigerprints.clemson.edu/all_dissertations Part of the Inorganic Chemistry Commons Recommended Citation Ranmohotti, Kulugammana gedera, "SYNTHESIS, STRUCTURE AND MAGNETIC PROPERTIES OF OXY-ANION BASED MAGNETIC SOLIDS CONTAINING TRANSITION METAL OXIDE NANOSTRUCTURES" (2008). All Dissertations. 289. https://tigerprints.clemson.edu/all_dissertations/289 This Dissertation is brought to you for free and open access by the Dissertations at TigerPrints. It has been accepted for inclusion in All Dissertations by an authorized administrator of TigerPrints. For more information, please contact [email protected]. SYNTHESIS, STRUCTURE AND MAGNETIC PROPERTIES OF OXY-ANION BASED MAGNETIC SOLIDS CONTAINING TRANSITION METAL OXIDE NANOSTRUCTURES A Dissertation Presented to the Graduate School of Clemson University In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Chemistry by Kulugammana Gedera Sanjaya Ranmohotti December 2008 Accepted by: Dr. Shiou-Jyh Hwu, Committee Chair Dr. William T. Pennington Dr. Murray S. Daw Dr. Julia L. Brumaghim ABSTRACT Inline with the focus of our research, my goal for this dissertation study is to further explore new classes of magnetic insulators exhibiting novel properties. The scope of this work is twofold: 1) the exploratory synthesis of polyanion-based mixed-framework compounds containing transition metal oxide magnetic nanostructures, and 2) the investigation of the structure/property correlation with respect to the spin couplings in confined lattices. These studies are of fundamental and technological importance regarding the long-term development of low-dimensional magnetic solids for device applications in especially information storage and quantum computing. Several interesting and significant transition metal based silicate, phosphate arsenate and vanadate compounds with structural frameworks featuring low-dimensional layers, chains, and oligomers were synthesized. Their synthesis and characterizations are outlined in this dissertation in the order of the size of the magnetic nanostructures following the introduction (Chapter 1) and experimental (Chapter 2) sections. The first project, as illustrated in Chapter 3, was undertaken for the attempted synthesis of the solid-solution series Cs 2-xRb xCu 3P4O14 ( x = 0, 0.33, 0.50, 0.80). The primary focus of this study is on the size effect of monovalent cation to the bulk magnetic properties. The second project was the exploratory synthesis of “nanostructured” manganese oxide materials. In this project, new manganese-based phosphates and arsenate systems have been explored. We were able to isolate several new and interesting compounds displaying interesting structures and properties. (Cs 3Cl)Mn 4O4(AsO 4)3 (Chapter 4) ii contains structurally isolated Mn 4O4 cubanes residing in each of the anti-ReO 3 type (Cs 3Cl) cages. The field dependent magnetic studies show superparamagnetic type behavior similarly found in magnetic nanoparticals. A new manganese phosphate compound, BaRb 3KMn 6(PO 4)6, adopting a new structure type reveals a novel “bangle”- like magnetic nanostructure unit (Chapter 5). Also, a new manganese(III) phosphate compound, Ba 2Mn 3O2(PO 4)3, exhibits structurally isolated nanowire (Chapter 6). This compound presents once again the utilities of closed-shell, nonmagnetic oxyanions for synthesizing structurally isolated and electronically insulated magnetic nanostructures. This study also allows us to further understand the issues concerning low-dimensional magnetic structures in extended solids, magnetic anisotropy, coherent length for magnetic coupling, and their relationships with quantum tunneling of magnetization, a well- recognized phenomenon in single molecule magnets (SMMs). The mixed-valance manganese(II,III) systems, such as Na 3Mn 7(AsO 4)6, KNaMn 3(AsO 4)3 (Chapter 7), µ3- oxo Ba 2CsRbMn 7O2(AsO 4)6 and µ4-oxo CsMn 3O(AsO 4)2 (Chapter 8), presents the complexity of spin interactions in compounds containing two-dimensional Mn-O lattices thus magnetic anomalies. The third project (Chapter 9) deals with a new series of fresnoite-type solids; Ba 2Mn(Mn 1.4 Si 0.6 O7)Cl, Rb 2MnV 2O7Cl and Cs 2MnV 2O7Cl, where noncentrosymmetric lattices and ferromagnetic properties are evident. This discovery offers opportunities for the search of new “multiferroic ” materials for device miniaturization. In summary, the man body of this dissertation reports the exploratory synthesis, structural characterization, and physical properties studies of selected chemical systems iii that contain magnetic nanostructures. The Appendix summarizes remaining new compounds discovered in this study that exhibit equally interesting features. iv ACKNOWLEDGMENTS With a deepest sense of gratitude, I would like to thank my advisor Dr. Shiou-Jyh Hwu for his guidance, support and encouragement throughout this study as he provided many insightful ideas and thoughts during my graduate career. In addition, I would like to thank my advisory committee members Dr. William T. Pennington, Dr. Murray S. Daw and Dr. Julia L. Brumaghim for serving on my thesis committee. I would like to extend my appreciation to Dr. Donald G. Vanderveer for his patience, time and effort helping me with crystal structure solutions. I also thank the Kolis group for their endless support throughout the years, the EM Lab at AMRL for their instrumentation and Chemistry Department at Clemson for the great assistance given to me. Financial support for this research by NSF is gratefully acknowledged. Concerning my group, I would like to thank both past and present Hwu group members for the help, assistance and friendship. I especially like thank Palmer West, Wendy Queen and Greg Becht for their valuable suggestions and making corrections in my dissertation. I also thank my parents for their endless love and faith in me through out these years though we were many miles apart. Most of all, thank you to my best friend and wife, Sanjeewanie, who helped me in keeping every thing in perspective and with out you, this life would have been much more difficult and I wouldn’t have made this far. v TABLE OF CONTENTS Page TITLE PAGE....................................................................................................................i ABSTRACT.....................................................................................................................ii ACKNOWLEDGMENTS ...............................................................................................v LIST OF TABLES..........................................................................................................xi LIST OF FIGURES ......................................................................................................xiv CHAPTER 1. INTRODUCTION .........................................................................................1 Literature Cited ............................................................................................35 2. EXPERIMENTAL METHODS AND CHARACTERIZATION TECHNIQUES ......................................................................................39 Solid State Synthesis and Crystal Growth ...................................................39 Single Crystal X-Ray Diffraction ..........................................................44 Powder X-Ray Diffraction.....................................................................46 UV-vis Diffuse Reflectance Spectroscopy ............................................48 Magnetic Susceptibility Measurements .................................................49 Energy Dispersion X-ray Analysis ........................................................52 Literature Cited ............................................................................................53 3. SYNTHESIS, STRUCTURE AND MAGNETIC PROPERTIES OF COPPER(II) PHOSPHATES CONTAINING PERIODIC ARRAYS OF STAGGERED SQUARE-PLANER CuO 4 TRIMERS................................55 Introduction..................................................................................................55 Synthesis and Characterization of Cs 2-xRb xCu 3P4O14 (0.0 ≤ x ≤ 0.8) ..........56 Synthesis ................................................................................................56 Characterization .....................................................................................56 vi Table of Contents (Continued) Page Results and Discussion ................................................................................64 Synthesis and Structure..........................................................................64 UV-Vis Diffuse Reflectance Spectroscopy ...........................................73 Magnetic Susceptibility .........................................................................73 Literature Cited ............................................................................................85 4. Mn 4O4 CUBANE IN ANTI-ReO 3 TYPE CESIUM CHLORIDE LATTICE: SYNTHESIS STRUCTURE AND MAGNETIC PROPERTIES OF NON- CENTROSYMMETRIC (Cs 3Cl)Mn 4O4(AsO 4)3 .........................................87 Introduction..................................................................................................87 Synthesis and Characterization