IMSE presents the North American Materials Colloquium Series:
For the link to the synchronous presentation and live Q&A session (10/01 2-3:15PM or 10/02 3-4:15PM): RSVP Here
Asynchronously view the presentation ONLY here: Asynchronous Presentation (link not live yet)
Two presentations will be given in today’s seminar slot:
Multiferroic Heterostructures by Design”
University of Wisconsin–Madison
Electric-field control of magnetic properties, i.e. the converse magnetoelectric (ME) effect, offers opportunities for both fundamental scientific research as well as the development of multifunctional devices.
In particular, strain driven ME coupling in ferroelectric (FE) / ferromagnetic (FM) heterostructures provides an encouraging route to realizing the next generation of low-power memory storage and sensing technologies. The key lies with the use of relaxor-ferroelectrics such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), whose giant piezoelectricity allows for large strains under an electric field. By coupling with a FM overlayer with large magnetostriction, transfer of strain from the FE into the FM can result in piezo-driven control of both the direction and strength of the FM’s in-plane magnetic anisotropy.
Achieving low-power means that thin films of PMN-PT must be used; however, their implementation faces two significant challenges: 1) Mechanical clamping by passive substrates nearly eliminates piezoelectricity in thin films. 2) Rotation of the in-plane anisotropy of the FM requires anisotropic in-plane strains. Our unique approach involves growth of (011) oriented epitaxial PMN-PT thin films, which can generate the desired uniaxial in-plane strains, followed by complete removal of the substrate to create PMN-PT membranes.
First, I will show how magnetoelectric coupling of the PMN-PT membranes with Ni overlayers results in piezo-driven control of the Ni layer’s magnetic anisotropy over a range of only 3V, two orders of magnitude lower than the 100s of volts required using bulk single crystal PMN-PT. I will also discuss how the PMN-PT membranes can be used to create novel heterostructures via the process of crystal stacking [Nature 578, 75–81 (2020)], circumventing obstacles posed by the conventional method of heteroepitaxy. This approach provides an innovative platform for the design and discovery of new strain-mediated phenomena.
Shane Lindemann is a graduate student in the Materials Science and Engineering Department at University of Wisconsin-Madison (UW). He received a B.S. in civil engineering at Louisiana State University (LSU) in 2015, where he also completed minors in physics and materials science that motivated him to pursue a Ph.D. in materials science.
He is a member of the UW Oxide Lab, under the advisement of Dr. Chang-Beom Eom, where his research focuses on studying the magnetoelectric coupling in multiferroic thin film heterostructures utilizing giant piezoelectricity. He co-authored six publications including one in Nature [“Heterogeneous Integration of single-crystalline complex-oxide membranes” Nature 578, 75 (2020)]. In this paper, Shane and his collaborators demonstrated the creation of artificial heterostructures through crystal-stacking, allowing for the combination of layers with different crystal structures that cannot be combined by conventional heteroepitaxy. Throughout his academic career, Shane enjoyed teaching/tutoring experiences in the LSU departments of math and physics, as an MCAT physics instructor with the Princeton Review, and as a TA for two courses (MSE 333 and 434) at UW-Madison..
“Solute Characterization of (Zr,Ta)B2 Ceramics”
Graduate Research Assistant and Ph.D. Candidate
Missouri University of Science and Technology
Solute segregation was examined in zirconium diboride and zirconium-tantalum diboride solid solution ceramics that were produced by reactive hot pressing. Microstructural analysis demonstrated that the ZrB2 and (Zr,Ta)B2 ceramics reached nearly full relative density and were nominally phase pure. X-ray diffraction was consistent with full incorporation of Ta into solid solution within the ZrB2 structure, and energy dispersive spectroscopy demonstrated that tantalum was well-distributed throughout the bulk of the Ta-doped specimens. The weak characteristic x-rays for B led to inaccurate results for total atom concentrations in boride ceramics by energy dispersive spectroscopy. Atom probe tomography was used to analyze the amount and spatial distribution of Ta species. No obvious Ta segregation was observed in grains or grain boundaries. However, nitrogen strongly segregated to a grain boundary. This study demonstrated that atom probe tomography is an accurate method for characterizing the amount and spatial distribution of metallic and non-metallic species in ZrB2 ceramics.
Anna Dorner is currently a 4th-year Ph.D. student in ceramic engineering at Missouri University of Science and Technology, where she is a member of the ultra-high temperature ceramics research group headed by Dr. Bill Fahrenholtz and Dr. Greg Hilmas. Her graduate research interests are based in fundamental science studies of solid solution diboride materials. Her first publication on the characterization of diboride solid solutions was published in the Journal of the American Ceramic Society in December 2019, and her current research includes the effects of solute additions upon mechanical properties in ZrB2 and phase equilibria and diffusion in the ZrB2-TaB2 system. Anna was awarded “Outstanding Ceramic Graduate Student” by her department in Spring 2019. Prior to her time at Missouri S&T, she attended Purdue University where she earned a B.S. in chemistry with minors in materials science and Spanish in 2017.