Kannan M. Krishnan | |
---|---|
Occupation(s) | Academic, author, entrepreneur, and artist |
Awards | Eli Franklin Burton Medal, Microscopy Society of America (1992) John Simon Guggenheim Foundation Fellowship (2004) Elected Member, Washington State Academy of Science (2009) Donald G. Fink Prize, IEEE (2012) Alexander von Humboldt Career Research Award, Alexander von Humboldt Foundation (2016) |
Academic background | |
Education | B. Tech in Mechanical Engineering MS in Materials Science & Engineering PhD in Material Science & Engineering |
Alma mater | Indian Institute of Technology, Kanpur State University of New York, Stony Brook University of California, Berkeley |
Academic work | |
Discipline | Materials scientist &engineer,physicist,bioengineer,and educator |
Institutions | University of Washington (UW) University of California,Berkeley (UCB) |
Kannan M. Krishnan is an Indian-American academic,author and entrepreneur. He is a Professor of Materials Science and Engineering,an Adjunct Professor of Physics, [1] and an Associate Faculty of the South Asia Centre,at the University of Washington,Seattle (UW). [2]
Krishnan has contributed to the field of biomedical nanomagnetics, [3] especially the applications of tailored magnetic biomaterials in medicine,emphasizing imaging,and therapy,and including their commercialization and clinical translations. He was also the first to develop a patented material architecture for semiconductor-magnetic device integration. He also identified a new class of materials ––dilute magnetic dielectrics [4] ––that are both ferromagnetic and insulating,and showed that the ferromagnetism in such materials is defect-mediated. [5] He is also a well-recognized teacher, [6] writing two textbooks,Fundamentals and Applications of Magnetic Materials (2016), [7] and Principles of Materials Characterization and Metrology (2021),both published by Oxford University Press. [8]
Krishnan is known in multiple disciplines for his scholarship,research,teaching,and mentoring. [9] His awards include the TMS Weertman Educator Award (2024),Alexander von Humboldt Forschungspreis (2016),the TMS Distinguished Engineer/Scientist (2015),IEEE Fink Prize (2012), [10] IEEE Magnetics Society Distinguished Lecturer (2009), [11] Fulbright Specialist (2010),Guggenheim (2004) and Rockefeller (2008) Fellowships,the Burton Medal (MSA,1992), [12] and the College of Engineering Outstanding Educator (UW,2004).
Krishnan is an elected member of the Washington State Academy of Sciences,and Fellow of the American Association for the Advancement of Science,the American Physical Society, [13] the Institute of Physics (London),and the Institute of Electrical and Electronics Engineers. [6] He has served on the editorial boards of the Journal of Magnetism &Magnetic Materials, Journal of Materials Science , [14] Acta Materialia ,Journal of Physics D:Applied Physics,IEEE Magnetics Letters and Medical Physics. In 2010,along with two graduate students,he started a company,LodeSpin Labs,to develop tailored magnetic carriers for a range of biomedical applications. [15]
Krishnan studied at Indian Institute of Technology,Kanpur,where he earned his Bachelor of Technology degree in Mechanical Engineering in 1978. [16] He then pursued his Master of Science in Materials Science &Engineering from the State University of New York,Stony Brook in 1980,and completed his Ph.D. in Materials Science &Engineering from the University of California,Berkeley in 1984,where he also minored in Physics and Mathematics. [17]
After completing his Ph.D. in 1984,Krishnan held various scientific and teaching positions at Lawrence Berkeley National Laboratory [18] and UC Berkeley, [19] before joining the University of Washington,in 2001,as the Campbell Chair Professor of Materials Sciences &Engineering and Adjunct Professor of Physics. He has also held visiting at multiple institutions including the Hitachi Central Research Laboratory (Japan),Tohoku University,University Klinikum-Eppendorf,Hamburg,University of Sao Paolo,University of Western Australia,University of Alexandria (Egypt),and the Indian Institute of Science. [2]
In addition to his academic work,from 2010 to 2020,Krishnan founded LodeSpin Labs,a startup company to develop tailored magnetic nanoparticles for diverse biomedical applications. [15] He holds five patents for his research. [20] [21] [22]
Krishnan's academic scholarship and research spans three areas. First being Condensed Matter Physics and Materials Science &Engineering,with a focus on nanoscale magnetic and transport phenomena in reduced dimensions,including their inter-coupling,to develop new paradigms for materials &devices in the context of novel information (storage,processing,and logic) and energy technologies. Second being Bioengineering at the intersection of Magnetism,Materials,and Medicine with an emphasis on diagnostics,imaging,and therapy,alongside translational research and commercialization activities. Third being Materials Characterization and Metrology,addressing structure-property correlations using electrons,photons,and scanning probes. [23]
Krishnan's first book,Fundamentals and Applications of Magnetic Materials (2016),is an interdisciplinary textbook on magnetism,magnetic materials,and related applications. Written in a pedagogical style,its chapters progress from the physics of magnetism,to magnetic phenomena in materials,to size and dimensionality effects,to applications. The second half of the book offers interdisciplinary discussions of information technology,magnetoelectronics,and the future of biomedicine via recent developments in magnetism. The book also includes relevant details of the chemical synthesis of small particles and the physical deposition of ultra-thin films. In addition,the book presents details of characterization methods and summaries of representative families of materials,including tables of properties. CGS equivalents (to SI) are included throughout the book. The book has received reviews,including:"The breadth and depth of the work is impressive,there are numerous clear illustrations,and extensive references to research literature up to 2016... For a teacher of advanced classes who needs real-world applications,or for an early-stage researcher looking for a wider context,this is a rich source. As an up-to-date guide to the technology of magnetic materials it excels."; [7] and "There are other books on similar topics,but this one is the most comprehensive in its wide and thorough coverage of applications ranging from magnetic storage to spintronics to bio-related applications... Despite the broad coverage of this book,most topics are discussed in depth... An excellent book for advanced undergraduate and graduate students,and researchers in the field." [24]
Krishnan's second book,Principles of Materials Characterization and Metrology (2021),is based on the premise that characterization enables a microscopic understanding of the fundamental properties of materials (Science) to predict their macroscopic behavior (Engineering). It combines a discussion of the physical principles and practical application of various characterization techniques,using electrons,photons,neutrons and scanning probes. A review in Contemporary Physics stated "This is an excellent textbook for a course on the structural characterization of materials. It could also find a place on the bookshelf of an experienced materials scientist wanting to be brought up to date on new techniques and their applications." [8]
Krishnan pioneered the colloidal synthesis of Co nanoparticles (NPs) with size and shape control [25] to tailor their magnetic properties,and extended this approach to synthesize phase-pure magnetite NPs,with near-ideal magnetization,by controlled oxidation during growth. He solved the problem of optimizing the a.c. magnetic response,in vivo,of iron-oxide NPs for any applied frequency:using Monte Carlo simulations he determined the optimal core size to be at the threshold of the superparamagnetic transition,synthesized the required NPs,and controlled their biocompatibility and inter-particle interactions with hydrophilic coatings of well-defined molecular size. With this approach,he pioneered the development of nanomagnetic tracers to achieve sub-mm resolution and nanogram sensitivity,in vivo,in Magnetic Particle Imaging (MPI) ––a new tracer-based,whole-body imaging technology with high contrast (no tissue background) and nanogram sensitivity. [15]
Krishnan's work in this area has led to the development of tunable mesoscale magnetic structures by nanoimprint lithography [26] and ion-beam patterning [27] technologies. [26] In addition to fabricating elements with unique three-dimensional shapes, [28] these patterned elements have provided fundamental insight into magnetic behavior at the nanoscale and the opportunity to design new architectures for magnetic quantum cellular automata [29] ––a new approach to creating magnetic logic gates and computing [30] without electrical current,artificial spin ice,and the emerging field of spin-orbitronics. [31] His work has also led to significant new materials and structures,including the first development of a patented material architecture [32] for semiconductor-magnetic device integration. [33]
Krishnan synthesize and studied ferromagnetism in transition-metal-doped wide band-gap semiconducting oxides. [34] [5] He identified a class of new materials ––dilute magnetic dielectrics [35] ––that are both ferromagnetic and insulating and showed that the ferromagnetism in such materials is defect-mediated. He also contributed to the understanding of transport mechanisms in colossal magnetoresistive oxides. [36]
Krishnan developed characterization methodologies for various materials,particularly using electron and photon probes,and [37] Early in his career,for his doctoral thesis at UC,Berkeley,he developed a technique,subsequently known as ALCHEMI, [38] combining the theory of inelastic scattering of fast electrons with experimental measurements and demonstrated the applicability of this technique,for determining the specific-site occupations of elements in a wide range of crystalline materials. [12] He has also developed and applied numerous imaging,spectroscopy and scattering methods,including the use of advanced characterization tools for this purpose using electrons (holography [39] [40] and electron energy-loss spectroscopy [41] ),photons (synchrotron radiation),and scanning probes. His contributions in this field include the first direct evidence for block-by-block growth of high-temperature superconductor ultra-thin films, [42] and studies of the scaling of interface roughness in magnetic superlattices at the atomic scale using element-specific energy filtered imaging. [43]
Ferromagnetism is a property of certain materials that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagnetic materials are noticeably attracted to a magnet, which is a consequence of their substantial magnetic permeability.
Superparamagnetism is a form of magnetism which appears in small ferromagnetic or ferrimagnetic nanoparticles. In sufficiently small nanoparticles, magnetization can randomly flip direction under the influence of temperature. The typical time between two flips is called the Néel relaxation time. In the absence of an external magnetic field, when the time used to measure the magnetization of the nanoparticles is much longer than the Néel relaxation time, their magnetization appears to be in average zero; they are said to be in the superparamagnetic state. In this state, an external magnetic field is able to magnetize the nanoparticles, similarly to a paramagnet. However, their magnetic susceptibility is much larger than that of paramagnets.
In physics and materials science, the Curie temperature (TC), or Curie point, is the temperature above which certain materials lose their permanent magnetic properties, which can (in most cases) be replaced by induced magnetism. The Curie temperature is named after Pierre Curie, who showed that magnetism was lost at a critical temperature.
Coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. Coercivity is usually measured in oersted or ampere/meter units and is denoted HC.
Iron(II,III) oxide, or black iron oxide, is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe2O3) which also occurs naturally as the mineral hematite. It contains both Fe2+ and Fe3+ ions and is sometimes formulated as FeO ∙ Fe2O3. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic, but is sometimes incorrectly described as ferromagnetic. Its most extensive use is as a black pigment (see: Mars Black). For this purpose, it is synthesized rather than being extracted from the naturally occurring mineral as the particle size and shape can be varied by the method of production.
Magnetic semiconductors are semiconductor materials that exhibit both ferromagnetism and useful semiconductor properties. If implemented in devices, these materials could provide a new type of control of conduction. Whereas traditional electronics are based on control of charge carriers, practical magnetic semiconductors would also allow control of quantum spin state. This would theoretically provide near-total spin polarization, which is an important property for spintronics applications, e.g. spin transistors.
Magnetic particle imaging (MPI) is an emerging non-invasive tomographic technique that directly detects superparamagnetic nanoparticle tracers. The technology has potential applications in diagnostic imaging and material science. Currently, it is used in medical research to measure the 3-D location and concentration of nanoparticles. Imaging does not use ionizing radiation and can produce a signal at any depth within the body. MPI was first conceived in 2001 by scientists working at the Royal Philips Research lab in Hamburg. The first system was established and reported in 2005. Since then, the technology has been advanced by academic researchers at several universities around the world. The first commercial MPI scanners have recently become available from Magnetic Insight and Bruker Biospin.
Multiferroics are defined as materials that exhibit more than one of the primary ferroic properties in the same phase:
Nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material.
Molecule-based magnets (MBMs) or molecular magnets are a class of materials capable of displaying ferromagnetism and other more complex magnetic phenomena. This class expands the materials properties typically associated with magnets to include low density, transparency, electrical insulation, and low-temperature fabrication, as well as combine magnetic ordering with other properties such as photoresponsiveness. Essentially all of the common magnetic phenomena associated with conventional transition-metal magnets and rare-earth magnets can be found in molecule-based magnets. Prior to 2011, MBMs were seen to exhibit "magnetic ordering with Curie temperature (Tc) exceeding room temperature".
Magnetic nanoparticles (MNPs) are a class of nanoparticle that can be manipulated using magnetic fields. Such particles commonly consist of two components, a magnetic material, often iron, nickel and cobalt, and a chemical component that has functionality. While nanoparticles are smaller than 1 micrometer in diameter, the larger microbeads are 0.5–500 micrometer in diameter. Magnetic nanoparticle clusters that are composed of a number of individual magnetic nanoparticles are known as magnetic nanobeads with a diameter of 50–200 nanometers. Magnetic nanoparticle clusters are a basis for their further magnetic assembly into magnetic nanochains. The magnetic nanoparticles have been the focus of much research recently because they possess attractive properties which could see potential use in catalysis including nanomaterial-based catalysts, biomedicine and tissue specific targeting, magnetically tunable colloidal photonic crystals, microfluidics, magnetic resonance imaging, magnetic particle imaging, data storage, environmental remediation, nanofluids, optical filters, defect sensor, magnetic cooling and cation sensors.
Iron oxide nanoparticles are iron oxide particles with diameters between about 1 and 100 nanometers. The two main forms are composed of magnetite and its oxidized form maghemite. They have attracted extensive interest due to their superparamagnetic properties and their potential applications in many fields including molecular imaging.
Magnonics is an emerging field of modern magnetism, which can be considered a sub-field of modern solid state physics. Magnonics combines the study of waves and magnetism. Its main aim is to investigate the behaviour of spin waves in nano-structure elements. In essence, spin waves are a propagating re-ordering of the magnetisation in a material and arise from the precession of magnetic moments. Magnetic moments arise from the orbital and spin moments of the electron, most often it is this spin moment that contributes to the net magnetic moment.
Spin engineering describes the control and manipulation of quantum spin systems to develop devices and materials. This includes the use of the spin degrees of freedom as a probe for spin based phenomena. Because of the basic importance of quantum spin for physical and chemical processes, spin engineering is relevant for a wide range of scientific and technological applications. Current examples range from Bose–Einstein condensation to spin-based data storage and reading in state-of-the-art hard disk drives, as well as from powerful analytical tools like nuclear magnetic resonance spectroscopy and electron paramagnetic resonance spectroscopy to the development of magnetic molecules as qubits and magnetic nanoparticles. In addition, spin engineering exploits the functionality of spin to design materials with novel properties as well as to provide a better understanding and advanced applications of conventional material systems. Many chemical reactions are devised to create bulk materials or single molecules with well defined spin properties, such as a single-molecule magnet. The aim of this article is to provide an outline of fields of research and development where the focus is on the properties and applications of quantum spin.
Magnetic material synthesis and characterization technology continue to improve, allowing for the production of various shapes, sizes, and compositions of magnetic material to be studied and tuned for improved properties. One of the places which has seen great advancement is in the synthesis of magnetic materials at nanometer length scales. Nanoparticle research has seen a great deal of interest in a number of fields as many phenomena can be explained by what is occurring on the nanoscale, which can be probed more effectively using nanometer sized materials. One unique type of materials which have seen a recent surge in research interest have been known as "nanoflakes" where they resemble flakes or discs of nanometer thickness and micrometer dimensions. Nanomaterials of this shape have seen use in a number of fields including energy storage, as [electrodes] of electrochemical cells, and in cancer therapy to kill cancer cells.
Iron–platinum nanoparticles are 3D superlattices composed of an approximately equal atomic ratio of Fe and Pt. Under standard conditions, FePt NPs exist in the face-centered cubic phase but can change to a chemically ordered face-centered tetragonal phase as a result of thermal annealing. Currently there are many synthetic methods such as water-in-oil microemulsion, one-step thermal synthesis with metal precursors, and exchanged-coupled assembly for making FePt NPs. An important property of FePt NPs is their superparamagnetic character below 10 nanometers. The superparamagnetism of FePt NPs has made them attractive candidates to be used as MRI/CT scanning agents and a high-density recording material.
Yuri Suzuki is a Professor of Applied Physics at Stanford University. She studies novel ground states and magnetic phenomena. She is a Fellow of the American Physical Society and an American Competitiveness and Innovation Fellow of the National Science Foundation.
Mohindar Singh Seehra is an Indian-American Physicist, academic and researcher. He is Eberly Distinguished Professor Emeritus at West Virginia University (WVU).
Sara A. Majetich is an American physicist and Professor of Physics at Carnegie Mellon University. Her work considers magnetic nanoparticles and nanostructures for application in spintronic devices. She is a Fellow of the American Physical Society and the Institute of Electrical and Electronics Engineers.
Bernard Dieny is a research scientist and an entrepreneur. He is Chief Scientist at SPINTEC, a CEA/CNRS/UGA research laboratory that he co-founded in 2002 in Grenoble, France. He is also co-founder of two startup companies: Crocus Technology on MRAM and magnetic sensors in 2006 and EVADERIS on circuits design in 2014.
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(help)$ Hole-Driven Conductivity in ${\mathrm{La}}_{1\ensuremath{-}\mathit{x}}{\mathrm{Sr}}_{\mathit{x}}{\mathrm{MnO}}_{3}$ $(0\ensuremath{\le}\phantom{\rule{0ex}{0ex}}\mathit{x}\phantom{\rule{0ex}{0ex}}\ensuremath{\le}0.7)$ and ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{\mathit{z}}$ Thin Films|first1=H. L.|last1=Ju|first2=H.-C.|last2=Sohn|first3=Kannan M.|last3=Krishnan|date=27 October 1997|journal=Physical Review Letters|volume=79|issue=17|pages=3230–3233|via=APS|doi=10.1103/PhysRevLett.79.3230}}