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,
Bioengineering at the intersection of
Magnetism,
Materials, and
Medicine with an emphasis on diagnostics, imaging, and therapy, alongside translational research and commercialization activities. And third,
Materials Characterization and
Metrology, addressing structure-property correlations using electrons, photons, and scanning probes.
Books 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."; 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." 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. and ion-beam patterning technologies. 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 –– a new approach to creating magnetic logic gates and computing without electrical current, artificial spin ice, and the emerging field of spin-orbitronics. His work has also led to significant new materials and structures, including the first development of a patented material architecture for semiconductor-magnetic device integration. Krishnan synthesized and studied ferromagnetism in transition-metal-doped wide band-gap semiconducting oxides. –– 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.
Materials characterization and metrology Krishnan developed characterization methodologies for various materials, particularly using electron and photon probes. Early in his career, for his doctoral thesis at UC, Berkeley, he developed a technique, subsequently known as ALCHEMI, 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. and electron energy-loss spectroscopy), 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, and studies of the scaling of interface roughness in magnetic superlattices at the atomic scale using element-specific energy filtered imaging. ==Awards and honors==