DOCSLIB.ORG

Thesis Research Has Been a Collaborative Effort, and I Must Thank All Those That Have Made My Dissertation Work Complete

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Thesis Research Has Been a Collaborative Effort, and I Must Thank All Those That Have Made My Dissertation Work Complete UNIVERSITY of CALIFORNIA Santa Barbara Magnetism in Transition-Metal-Substituted Semiconducting Oxides A Dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Materials by Aditi S. Risbud Committee in charge: Professor Ram Seshadri, Chair Professor Anthony K. Cheetham Professor Nicola A. Spaldin Professor Juergen Eckert September 2005 The dissertation of Aditi S. Risbud is approved. Professor Anthony K. Cheetham Professor Nicola A. Spaldin Professor Juergen Eckert Professor Ram Seshadri, Committee Chair August 2005 Magnetism in Transition-Metal-Substituted Semiconducting Oxides Copyright c 2005 by Aditi S. Risbud iii for my parents iv Acknowledgements Often as a chapter in one’s life comes to a close, an appreciation for what is about to be lost begins to surface. It is a credit to Santa Barbara that from the moment of my arrival, I was aware of how fortunate I would be to complete my Ph.D. work in such a beautiful environment. This work would not have been possible without the help of my advisor, Ram Seshadri, who I thank for being a wonderful advisor these past few years. Ram’s enthusiasm and re- lentless curiosity about science has been an inspiration, and I appreciate all his guidance over my time here. I must also (grudgingly) admit that I am now a Linux user, and happy about it. My thesis research has been a collaborative effort, and I must thank all those that have made my dissertation work complete. Nicola Spaldin’s sup- port throughout my thesis has been invaluable; on top of that, she is proba- bly the coolest professor I know. Thanks for the careful reading of my thesis. Gavin Lawes’ straightforward and innovative description of the magnetic be- v havior of my materials systems lent valuable insight into my research. Lauren Snedeker was a fantastic intern, cheerily plugging away in the lab and helping my thesis work along. Mentoring is a highly rewarding part of science and I was happy to work with Lauren, Margaret MacRae and Rey Honrada dur- ing my time here. Many thanks to my committee members Tony Cheetham, Juergen Eckert, and David Clarke for their input and suggestions. I must also thank Z.Q. Chen, S. Stemmer, J.P. Attfield, J. Ensling, C. Felser, M.M. Elcombe, and A.P. Ramirez for their contributions. Before I began my Ph.D. work, there were a number of individuals who helped in the development of my science abilities. My undergraduate advisor at UC Davis, Alexandra Navrotsky, has an amazing devotion to science, and I thank her for inspiring me to pursue my doctoral degree. I also thank Kate Helean for her mentoring and friendship. My next research stint at Caltech was guided by Harry Atwater. Harry’s ability to communicate science effec- tively resounded with me and sparked the motivation for my current career goal. I also thank Regina Ragan for being a great mentor and role model dur- ing my time at Caltech. Upon my arrival at UCSB, the Lange group allowed me to make a seamless transition to the Materials department, and I thank Fred Lange, Geoff & Denice Fair, Mark & Nicole Snyder, Biao and Zhou, Ryan Bock, Scott Fillery, Haksung Moon, and Lars Loeffler for their support and vi friendship. Dave Andeen is probably the best officemate I have ever had, and I will miss our conversations about Barry Switzer, the Raiders, Kings, and stay- ing cool, Lakers-style. The Seshadri group has seen a few members come and go in its relative youth, and I thank our post-docs K. Ramesha and Ombretta Masala for their help with magnetic measurements and electron microscopy. Eric Toberer and I have spent far too much time together being officemates and the only graduate students in the Seshadri group, most memorably at MRS Boston, home of the world’s best public transportation Kit Kat. As for MRS San Francisco- I’m sorry about those contact lenses. I will miss our fashion and color scheme discussions. Someday we’ll compile that list of quotes and pass it on to future group members. The best part of graduate school has been all the great people I have spent time with, both on and off the court. Jenny Andrew has been a source of endless friendship, replete with silly accents, Bollywood dance sequences, kothimbeer-laden meals, and lame materials science jokes. Tu kasli whooshaar ahes! Thanks for sitting through all my practice talks (and the real ones too). Michael Pontin helped me see the conspiracies of the world, and even though he projects ’bitter old man,’ he is one of the kindest, most thoughtful people I know. David Follman has been a great housemate and friend. He is a talented writer and a tolerant individual, especially during basketball season. Adam vii Pyzyna was a fun housemate and friend, and I will miss watching Chappelle and discussing the latest hip-hop scoop. Emily Parker has been a great friend, workout buddy (only a good friend would be willing to come to Sean’s brutal spin class and save seats) and sounding board for all my ridiculous drama. Remember: You are a Genius. Seth Boeshore has been a fine source of South Park quotes and car bomb synergy. Over many a coffee, he has continually surprised me with his intellect (beyond just science) and sharp personal ob- servations. Weak. Thanks also to Garrett Cole for discussions on excitons, book hoarding, and general science enthusiasm. Katie Schaefer has been a great friend, shopping buddy (a convert, in fact) and listener, letting me whine about my day over a coffee (just not iced) or lunch. Justin Abramson is prob- ably the worst officemate but most interesting friend I’ve had- I will miss our discussions from science to life philosophies. You’ve certainly taught me a thing or two about myself, and I appreciate that. Also, thanks for all your help with SC. Larken Euliss was our favorite non-Materials person- thanks for in- troducing me to GVAC, bumble & bumble, and ‘thinking in chapters.’ Good luck at UT Arlington! I must also thank the Materials girls: Felicia Pitek, Lisa Kinder, Meghan Kerner, Molly Gentleman and Lori Callaghan for a great time, whether it was dancing downtown or in Vegas. There are a few people who let me ignore them for months and then are viii willing to talk to me when we finally see each other. I call them long-distance friends. Stephanie Moore introduced me to Travis, dressing red, and Jude Law. She’s a great friend and an Australian, but I don’t hold that against her. Nils-Eric Snekkevik has been a great friend, e-mailing from all over the world and allowing me to vent about grad school, career paths, and singing along to Coldplay. Julie Casperson (now Brewer) has been a wonderful support through Caltech and grad school, managing to give me advice about school, shoes, and boys in a single afternoon. Thanks for including me in your wed- ding. Jason Holt has been a good friend over the years as well, in the homes of the Lakers, Warriors, and Kings. At least we can make fun of the Clippers together. I also thank Chelsea McClain, Malini Jain, Sean Chen, Sonia Dass, and Jay Young for their friendships over the years. I must now thank the people without whom I wouldn’t have made it where I am today. My cousin Sarita and I have grown up together, whether it was in one house or across continents. She has been there through every event (ex- cept when her phone dies) of my life, from our crazy family reunions to con- ventions and college experiences (unfortunately G Street cannot compete with 6th Street) with her own brand of sarcasm. She is the closest thing I have to a sister, and I hope that never changes. Thanks also to Seema, Raja, Vikram, and Himaunshu for being sibling stand-ins and playing basketball (or football, it’s ix hard to tell sometimes) in that crazy Oklahoma heat. Go Sooners! Finally, I thank my mom and dad, Smita and Subhash Risbud, for being my true best friends in this world. Dad has kept up with every science project or goal I have every pursued, often sending me articles or newspaper clippings to read, proofreading my work, patiently listening no matter what the situation, sci- ence or otherwise. Mom is tireless, and has always been willing to go have fun at any time of day or night, chat about friends and family, and told me what I needed to hear (even if I didn’t want to hear it). She is definitely the genetic source of my sense of humor. I especially appreciate all the trips you guys have made to SLO, driving the entire day so that we could spend an afternoon together, bringing me Co-op cookies. I am a very lucky girl. As it comes to a close, I am happy to say that this chapter of my life has been one of the most rewarding and enjoyable, and I wouldn’t trade it for a thing. x Curriculum Vitæ Aditi S. Risbud Education 1996-2000 B.S. in Materials Science and Engineering University of California, Davis Davis, CA 2001-2005 Ph.D. Materials University of California, Santa Barbara Santa Barbara, CA Publications A. S. Risbud, R. Seshadri, J. P. Ensling, and C. Felser. Dilute Ferrimagnetic Semiconductors in Fe-substituted Spinel ZnGa2O4. Journal of Physics: Condensed Matter, 17, 1003 (2005). G. Lawes, A. S. Risbud, A. P. Ramirez, and R. Seshadri. Absence of ferromagnetism in Co and Mn substituted polycrystalline ZnO.
Load more

Recommended publications
  • Lattice Location of Mn in Gaas and Gan Is Studied, Two Model Materials from Respectively the Narrow-Gap and Wide-Gap DMS Families
    FACULTEIT WETENSCHAPPEN Lattice location of Mn in GaAs and GaN Arnaud De Coster CERN-THESIS-2015-253 26/06/2015 Promotor: Prof. L.M.C.Pereira Proefschrift ingediend tot het Co-promotor: K. Temst behalen van de graad van Co-promotor: A. Vantomme Master of Science in Physics Academiejaar 2014-2015 i c Copyright by KU Leuven Without written permission of the promotors and the authors it is forbidden to reproduce or adapt in any form or by any means any part of this publication. Requests for obtaining the right to reproduce or utilize parts of this publication should be addressed to KU Leuven, Faculteit Wetenschappen, Geel Huis, Kasteelpark Arenberg 11 bus 2100, 3001 Leuven (Heverlee), Telephone +32 16 32 14 01. A written permission of the promotor is also required to use the methods, products, schematics and programs described in this work for industrial or commercial use, and for submitting this publication in scientific contests. Acknowledgement "To envision us coming up and pounding on this door, pounding and pound- ing, not just wanting admission but needing it, we don't know what it is but we can feel it, this total desperation to enter, pounding and pushing and kicking, etc. That, finally, the door opens...and it opens outward: we've been inside what we wanted all along. Das ist komisch." David Foster Wallace "It's not about the destination but about the journey". While too trite a quote to place above this acknowledgement, trite tends to hold true and it certainly holds for this thesis. Among the many people who helped me out along the way of this journey I want to first sincerely thank Professor Pereira for introducing me to the topic and emission channeling.
    [Show full text]
  • Ferromagnetism in II–VI Diluted Magnetic Semiconductor Zn1−Xcrxte H
    Ferromagnetism in II–VI diluted magnetic semiconductor Zn1−xCrxTe H. Saito, W. Zaets, S. Yamagata, Y. Suzuki, and K. Ando Citation: J. Appl. Phys. 91, 8085 (2002); doi: 10.1063/1.1452649 View online: http://dx.doi.org/10.1063/1.1452649 View Table of Contents: http://jap.aip.org/resource/1/JAPIAU/v91/i10 Published by the American Institute of Physics. Related Articles Tunneling time and Hartman effect in a ferromagnetic graphene superlattice AIP Advances 2, 012123 (2012) Phase dependent room-temperature ferromagnetism of Fe-doped TiO2 nanorods AIP Advances 2, 012107 (2012) Engineering magnetic domains in manganite thin films by laser interference Appl. Phys. Lett. 100, 012403 (2012) Size effect on magnetic coupling in all-ferromagnetic superlattices Appl. Phys. Lett. 99, 263108 (2011) Weak d0 magnetism in C and N doped ZnO J. Appl. Phys. 110, 123917 (2011) Additional information on J. Appl. Phys. Journal Homepage: http://jap.aip.org/ Journal Information: http://jap.aip.org/about/about_the_journal Top downloads: http://jap.aip.org/features/most_downloaded Information for Authors: http://jap.aip.org/authors Downloaded 24 Jan 2012 to 150.29.211.127. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions JOURNAL OF APPLIED PHYSICS VOLUME 91, NUMBER 10 15 MAY 2002 Magnetic Semiconductors II Olle G. Heinonen, Chairman Ferromagnetism in II–VI diluted magnetic semiconductor Zn1ÀxCrxTe H. Saito,a),b) W. Zaets, S. Yamagata,c) Y. Suzuki,b) and K. Ando Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, Japan Magnetic and transport properties of an epitaxial film of ferromagnetic II–VI diluted magnetic ͑ ͒ ϭ semiconductor DMS Zn1ϪxCrxTe ( x 0.035) were investigated.
    [Show full text]
  • Hidden Order Revealed Dilute Magnetic Semiconductors Such As Gallium Manganese Arsenide Could Be Key to the Development of Spintronics
    news & views DILUTE MAGNETIC SEMICONDUCTORS Hidden order revealed Dilute magnetic semiconductors such as gallium manganese arsenide could be key to the development of spintronics. But the relationship between electronic transport and magnetic properties has been hotly debated. Data indicating the preservation of the non-magnetic character of the host material provide startling new insight. Michael E. Flatté magine striking a golf ball from a tee states may become high enough to form Ordinarily, electric current moves in the middle of a dense forest. !e ball extended-like states, contributing su&cient through ferromagnetic (Ga,Mn)As like a Iwould hit leaves, branches and trunks carriers to screen the disorder and allow golf ball that’s being continually hit through in rapid progression and not travel far. coherent charge transport similar to that a forest — slowly and incoherently. To But if the ball were hit from a tee on a associated with valence-band conduction. study the transport characteristics and platform suspended above the trees, it !e nature of the transport and electronic structure of the states in this would be free to "y considerably further. electronic structure in the prototypical material above the Fermi energy, Ohya A similar demonstration has now been dilute magnetic semiconductor (Ga,Mn) and co-workers1 constructed a series performed by Ohya et al. within the As has been the subject of lengthy debate. of resonant tunnelling diodes in which dilute magnetic semiconductor gallium At high levels of manganese doping, the carriers are injected from a non-magnetic manganese arsenide, (Ga,Mn)As, as material exhibits some extended-state semiconductor into a (Ga,Mn)As quantum reported in Nature Physics1.
    [Show full text]
  • And Momentum-Resolved Electronic Structure of the Dilute Magnetic Semiconductor Manganese Doped Gallium Arsenide
    ARTICLE DOI: 10.1038/s41467-018-05823-z OPEN Element- and momentum-resolved electronic structure of the dilute magnetic semiconductor manganese doped gallium arsenide Slavomír Nemšák1,2,3,9, Mathias Gehlmann1,2,3, Cheng-Tai Kuo 1,2, Shih-Chieh Lin1,2, Christoph Schlueter4,10, Ewa Mlynczak 3, Tien-Lin Lee4, Lukasz Plucinski3, Hubert Ebert5, Igor Di Marco6,7, Ján Minár8, Claus M. Schneider 1,3 & Charles S. Fadley1,2 1234567890():,; The dilute magnetic semiconductors have promise in spin-based electronics applications due to their potential for ferromagnetic order at room temperature, and various unique switching and spin-dependent conductivity properties. However, the precise mechanism by which the transition-metal doping produces ferromagnetism has been controversial. Here we have studied a dilute magnetic semiconductor (5% manganese-doped gallium arsenide) with Bragg-reflection standing-wave hard X-ray angle-resolved photoemission spectroscopy, and resolved its electronic structure into element- and momentum- resolved components. The measured valence band intensities have been projected into element-resolved components using analogous energy scans of Ga 3d,Mn2p, and As 3d core levels, with results in excellent agreement with element-projected Bloch spectral functions and clarification of the electronic structure of this prototypical material. This technique should be broadly applicable to other multi-element materials. 1 Department of Physics, University of California, 1 Shields Ave, Davis, CA 95616, USA. 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA 94720, USA. 3 Peter-Grünberg-Institut PGI-6, Forschungszentrum Jülich, Jülich 52425, Germany. 4 Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK.
    [Show full text]
  • The Magnetic Behavior of Diluted Magnetic Semiconductors
    The magnetic behavior of diluted magnetic semiconductors Citation for published version (APA): Swagten, H. J. M. (1990). The magnetic behavior of diluted magnetic semiconductors. Technische Universiteit Eindhoven. https://doi.org/10.6100/IR340473 DOI: 10.6100/IR340473 Document status and date: Published: 01/01/1990 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.
    [Show full text]
  • Synthesis, Characterization and Promising Properties of Fe3o4/Cdse Nanocomposite
    EPJ Web of Conferences 201, 02002 (2019) https://doi.org/10.1051/epjconf/201920102002 AYSS-2018 Synthesis, characterization and promising properties of Fe3O4/CdSe nanocomposite Shaimaa A.Habib1,*, Mona B.Mohamed2, Samia A.Saafan1, and Talaat M.Meaz1 1Physics Department, Faculty of Science, Tanta University, Tanta, Egypt. 2Chemistry Department, National Institute of Laser Enhanced Sciences, Cairo University, Cairo, Egypt. Abstract Nowadays there is a continuously increasing worldwide concern for the utilization of magnetic semiconductor nanocomposites. We synthesized bifunctional magnetic–luminescent nanocomposites with Fe3O4 nanoparticles as the cores and CdSe as the shells by a facile direct precipitation method. Transmission electron microscopy (TEM) images revealed that the obtained bifunctional nanocomposites had a core–shell structure, in a spherical shape with a particle radius of about 10.3nm, and the shell thickness of about 2.2nm. The flower shape is due to the inhomogeneous growth of CdSe due to the presence of many active sites which turn to be nucleation centers for the CdSe on the surface of the nano-magnetite. The X-ray diffraction (XRD) patterns showed a cubic spinel structure of the Fe3O4 core. Magnetic measurements indicated that the presence of CdSe in the composite reduces its magnetic properties. Optical measurements of the Fe3O4/CdSe nanocomposite show that the prepared samples have dual functions, optical tunable band gap of the semiconductor quantum dots and the magnetic properties of magnetite. This type of composites would be considered as dilute magnetic semiconductors (DMS). 1 Introduction The term “nanocomposite” is used in the study of multiphase material where at least one of the constituent phases has one dimension less than 100 nm [1].
    [Show full text]
  • Manganese-Based Room Temperature Ferromagnetism in Gallium Arsenide
    OPTOELECTRONICS AND ADVANCED MATERIALS – RAPID COMMUNICATIONS Vol. 6, No. 11-12, Nov. – Dec. 2012, p. 1054 - 1060 Manganese-based room temperature ferromagnetism in gallium arsenide V. VASILACHE, N. G. APOSTOLa, G. A. LUNGUa, D. MACOVEIa, C. M. TEODORESCU*,a "Stefan cel Mare" University of Suceava, University Str. 13, 720229 Suceava, Romania aNational Institute of Materials Physics, P.O. Box MG-7, 077125, Magurele-Ilfov, Romania Manganese is deposited onto GaAs(001) substrates in high vacuum conditions (10-7 hPa), with substrates held at 300 °C. It is shown that this procedure yields to the diffusion of magnanese into gallium arsenide and the formation of a layer which exhibits room temperature ferromagnetism, with highly diluted Mn (below 1 atomic percent). X-ray absorption fine structure determinations at the Mn and Ga K-edges evidenced that Mn is not placed into substitutional Ga sites in GaAs. Most probably, Mn forms MnO clusters with rocksalt local structure. These clusters are the origin of the detected ferromagnetism. (Received October 22, 2012; accepted October 30, 2012) Keywords: Manganese, Gallium arsenide, MOKE, Ferromagnetism, X-ray absorption fine structure, EXAFS 1. Introduction (from Cr to Ni) and the literature of these systems is quite vast [17-19]. However, the simultaneous fulfilment of all Diluted magnetic semiconductors (DMS) are requirements (i-iv) from above is rather difficult and the intensively studied since more than two decades. The origin of the ferromagnetism in such structures is still a original work of Ohno, Munekata and coworkers debate [17]. In some cases, oxide superparamagnetic concentrated on manganese doped GaAs [1-4] and particles are formed [18], whereas in other cases the oxide manganese doped InAs [5-7].
    [Show full text]
  • And Momentum-Resolved Electronic Structure of the Dilute Magnetic Semiconductor Manganese Doped Gallium Arsenide
    UC Davis UC Davis Previously Published Works Title Element- and momentum-resolved electronic structure of the dilute magnetic semiconductor manganese doped gallium arsenide. Permalink https://escholarship.org/uc/item/4558r9m8 Journal Nature communications, 9(1) ISSN 2041-1723 Authors Nemšák, Slavomír Gehlmann, Mathias Kuo, Cheng-Tai et al. Publication Date 2018-08-17 DOI 10.1038/s41467-018-05823-z Peer reviewed eScholarship.org Powered by the California Digital Library University of California ARTICLE DOI: 10.1038/s41467-018-05823-z OPEN Element- and momentum-resolved electronic structure of the dilute magnetic semiconductor manganese doped gallium arsenide Slavomír Nemšák1,2,3,9, Mathias Gehlmann1,2,3, Cheng-Tai Kuo 1,2, Shih-Chieh Lin1,2, Christoph Schlueter4,10, Ewa Mlynczak 3, Tien-Lin Lee4, Lukasz Plucinski3, Hubert Ebert5, Igor Di Marco6,7, Ján Minár8, Claus M. Schneider 1,3 & Charles S. Fadley1,2 1234567890():,; The dilute magnetic semiconductors have promise in spin-based electronics applications due to their potential for ferromagnetic order at room temperature, and various unique switching and spin-dependent conductivity properties. However, the precise mechanism by which the transition-metal doping produces ferromagnetism has been controversial. Here we have studied a dilute magnetic semiconductor (5% manganese-doped gallium arsenide) with Bragg-reflection standing-wave hard X-ray angle-resolved photoemission spectroscopy, and resolved its electronic structure into element- and momentum- resolved components. The measured valence band intensities have been projected into element-resolved components using analogous energy scans of Ga 3d,Mn2p, and As 3d core levels, with results in excellent agreement with element-projected Bloch spectral functions and clarification of the electronic structure of this prototypical material.
    [Show full text]
  • Synthesis and Characterization of Dilute Magnetic Semiconductor Nanoparticles Donny Magana
    Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2007 Synthesis and Characterization of Dilute Magnetic Semiconductor Nanoparticles Donny Magana Follow this and additional works at the FSU Digital Library. For more information, please contact [email protected] THE FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES SYNTHESIS AND CHARACTERIZATION OF DILUTE MAGNETIC SEMICONDUCTOR NANOPARTICLES By DONNY MAGANA A Dissertation submitted to the Department of Chemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy Degree Awarded: Fall Semester, 2007 The members of the Committee approve the Dissertation of Donny Magana defended on August 30, 2007. Geoffrey F. Strouse Professor Directing Dissertation Stephan von Moln´ar Outside Committee Member Naresh Dalal Committee Member Sir Harold Kroto Committee Member The Office of Graduate Studies has verified and approved the above named committee members. ii To my parents, whose struggle made this journey possible. iii ACKNOWLEDGEMENTS Life adventures are nothing without the people that help along the way. My graduate decade 2 would have been far less adventurous without moving literally across the US to the great state of Florida. Without this experience I would have missed on a plethora of new friends and colleagues. I would like to thank Professor Geoff Strouse for keeping me on my toes these five years. For teaching me more than just research and for giving me the opportunity to learn the vast amount of research techniques I now know. My committee for the help, patience, and the knowledge you were always willing to give. I would like to thank my family for listening to all of my complaints even if they were small.
    [Show full text]
  • Effects of Cr and Fe Co-Doping on Structural, Optical, Electrical and Magnetic Properties of Titanium Dioxide (Tio2)
    Materials Science-Poland, 33(3), 2015, pp. 508-514 http://www.materialsscience.pwr.wroc.pl/ DOI: 10.1515/msp-2015-0092 Effects of Cr and Fe co-doping on structural, optical, electrical and magnetic properties of titanium dioxide (TiO2) SALMA WASEEM1∗,SAFIA ANJUM1,LUBNA MUSTAFA1,ANUM DAR2,FAROOQ BASHIR2, REHANA ZIA1 1Department of Physics, Lahore College for Women University, Lahore, Pakistan 2Central Lab, Lahore College for Women University, Lahore, Pakistan A series of Ti0:9Fe0:1−xCrxO2 (where x = 0.0, 0.02, 0.04, 0.6, 0.08, 0.10) was synthesized using the powder metallurgy route. The structural, morphological, magnetic, optical and electrical properties were investigated by X-ray diffractometry (XRD), Raman spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), UV-Vis spec- troscopy and four probe technique, respectively. The rutile phase was confirmed by XRD analysis which was also verified by Raman spectroscopy. It was observed that the grain size increased as the concentration of Cr increased. M-H loops ex- tracted from VSM analysis revealed anti-ferromagnetic, weak ferromagnetic and paramagnetic behaviors at room temperature. The band gap energy and resistivity measurements exhibited the semiconducting nature of Ti0:9Fe0:1−xCrxO2 based diluted magnetic semiconductors. Keywords: dilute magnetic semiconductors; rutile; grain size; magnetic properties; resistivity © Wroclaw University of Technology. 1. Introduction in these oxide DMSs is still controversial as to whether it is caused by electron spins or it stems Diluted magnetic semiconductors (DMS) con- from magnetic precipitations due to dopant ions sist of non magnetic semiconductor materials segregation [5]. doped with a few atomic percent of transition met- Among oxide based diluted magnetic semi- als.
    [Show full text]
  • Analysis of Structural, Morphological and Magnetic Properties of Diluted Magnetic Semiconductor Zno:Eu Obtained by Combustion Reaction
    Cerâmica 66 (2020) 262-268 http://dx.doi.org/10.1590/0366-69132020663792882 262 Analysis of structural, morphological and magnetic properties of diluted magnetic semiconductor ZnO:Eu obtained by combustion reaction (Análise das propriedades estruturais, morfológicas e magnéticas do semicondutor magnético diluído ZnO:Eu obtido via reação de combustão) D. B. Maia1*, R. A. Raimundo2,3, T. A. Passos1, R. A. Torquato1 1Federal University of Paraíba, Department of Materials Engineering, João Pessoa, PB, Brazil 2Federal University of Paraíba, Graduate Program in Mechanical Engineering, João Pessoa, PB, Brazil 3Federal University of Rio Grande do Norte, Department of Theoretical and Experimental Physics, Natal, RN, Brazil Abstract Eu-doped semiconductor matrix of ZnO at concentrations of 0.05 and 0.10 mols was synthesized by combustion reaction, using zinc nitrate, europium nitrate, and urea as fuel. In order to analyze the effect of europium concentration and sintering on the structure, band gap, magnetic and morphological properties of ZnO, the samples were sintered at 1100 °C for 30 min and analyzed before and after sintering via X-ray diffraction, ultraviolet and visible spectroscopy, vibrant sample magnetometry, and scanning electron microscopy. From the results obtained, it was found that there was the formation of the semiconductor phase ZnO and also a second- phase (Eu2O3). It was observed that the samples before and after sintering presented band gap values within the semiconductor range and ferromagnetism at room temperature. Keywords: diluted magnetic semiconductor, combustion reaction, zinc oxide, europium. Resumo Matriz semicondutora de ZnO, dopada com Eu nas concentrações de 0,05 e 0,10 mols, foi sintetizada por reação de combustão utilizando nitrato de zinco, nitrato de európio e ureia como combustível.
    [Show full text]
  • Manganese Doping for Enhanced Magnetic Brightening and Circular Polarization Control of Dark Excitons in Paramagnetic Layered Hybrid Metal-Halide Perovskites
    ARTICLE https://doi.org/10.1038/s41467-021-23602-1 OPEN Manganese doping for enhanced magnetic brightening and circular polarization control of dark excitons in paramagnetic layered hybrid metal-halide perovskites Timo Neumann1,2, Sascha Feldmann 1, Philipp Moser2, Alex Delhomme3, Jonathan Zerhoch2, Tim van de Goor 1, Shuli Wang4, Mateusz Dyksik 4,5, Thomas Winkler 1, Jonathan J. Finley 2, ✉ Paulina Plochocka 4,5, Martin S. Brandt2, Clément Faugeras 3, Andreas V. Stier2 & Felix Deschler 2 1234567890():,; Materials combining semiconductor functionalities with spin control are desired for the advancement of quantum technologies. Here, we study the magneto-optical properties of novel paramagnetic Ruddlesden-Popper hybrid perovskites Mn:(PEA)2PbI4 (PEA = phe- nethylammonium) and report magnetically brightened excitonic luminescence with strong circular polarization from the interaction with isolated Mn2+ ions. Using a combination of superconducting quantum interference device (SQUID) magnetometry, magneto-absorption and transient optical spectroscopy, we find that a dark exciton population is brightened by state mixing with the bright excitons in the presence of a magnetic field. Unexpectedly, the circular polarization of the dark exciton luminescence follows the Brillouin-shaped magneti- zation with a saturation polarization of 13% at 4 K and 6 T. From high-field transient magneto-luminescence we attribute our observations to spin-dependent exciton dynamics at early times after excitation, with first indications for a Mn-mediated spin-flip process. Our findings demonstrate manganese doping as a powerful approach to control excitonic spin physics in Ruddlesden-Popper perovskites, which will stimulate research on this highly tuneable material platform with promise for tailored interactions between magnetic moments and excitonic states.
    [Show full text]