Magneto-Electric Interactions in Ferromagnetic and Ferroelectric Core-Shell Nanofibers

29th October 2021

Timing : 1 pm EST

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Ferromagnetic-ferroelectric composites are of interests for studies on the nature of interactions between the two phases and for applications in useful technologies. The interactions are aided by mechanical forces, i.e., magnetostriction in the ferromagnet in a magnetic field and piezoelectric deformation in the ferroelectric in an electric field. The magneto-electric (ME) effects have been studied in a variety of composites systems in recent years and reports included observation of a giant ME at low frequencies and at frequencies corresponding to resonance modes. Devices such as sensors of magnetic fields, dual electric and magnetic field tunable microwave devices, and gyrators capable of current-to-voltage conversion have been demonstrated.
Since the strength of ME coupling depends critically on efficient transfer of strain generated by a magnetic- (or electric-) field in one phase to the other, one can accomplish a significant enhancement in the coupling strength in a nanocomposite in which the ratio of surface area-to-volume is orders of magnitude higher than in bulk or thick film composites. Coaxial nanofibers are of particular interest since they are free of substrate clamping effects one encounters in bilayers or nanopillars on a substrate.
This presentation will focus on the synthesis of coaxial nanofibers of spinel or hexagonal ferrites and ferroelectric barium titanate or lead zirconate titanate (PZT) by electrospinning techniques, assembly of the fibers into superstructures in a magnetic field and measurements of strengths of ME interactions. Core-shell fibers with an average diameter of 0.2-1.5 micron were prepared and characterized in terms of structure by scanning electron microscopy and scanning microwave microscopy. Studies on ME coupling in the magnetic field assembled films and a single nanofiber were carried out for excitation fields at frequencies from a Hz to 36 GHz and provide evidence for strong ME interactions in the fibers.




Snow
Gopalan Srinivasan
Distinguished Professor, Physics
Oakland University, Michigan
Gopalan Srinivasan is a Distinguished Professor of Physics at Oakland University in Michigan. He graduated with a PhD from Indian Institute of Technology-Bombay (India) and was a Research Associate at West Virginia University and a Research Professor at Colorado State University. He joined Oakland University in 1988. Gopalan’s research interests are the physics of multiferroics, magneto-electric effects in composites, and applications for sensors and signal processing devices. His research projects are supported by grants from the National Science Foundation and the DoD funding agencies. He has 4 patents, 340 publications, and more than 18,000 citations.