Ferroelectronics Lab

Understanding and utilizing non-volatile properties of materials

New Publication! “Signatures of quantum spin liquid state and unconventional transport in thin film TbInO3”

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Abstract: Quantum spin liquids, where the frustrated magnetic ground state hosts highly entangled spins resisting long-range order to 0 K, are exotic quantum magnets proximate to unconventional superconductivity and candidate platforms for topological quantum computing. Although several quantum spin liquid material candidates have been identified, thin films crucial for device fabrication and further tuning of properties remain elusive. Recently, hexagonal TbInO3 has emerged as a quantum spin liquid candidate which also hosts improper ferroelectricity and exotic high-temperature carrier transport. Here, we synthesize thin films of TbInO3 and characterize their magnetic and electronic properties. Our films present a highly frustrated magnetic ground state without long-range order to 0.4 K, consistent with bulk crystals. We further reveal a rich ferroelectric domain structure and unconventional non-local transport near room temperature, suggesting hexagonal TbInO3 as a promising candidate for realizing exotic magnetic and transport phenomena in epitaxial heterostructures.

Read more at Nature Communications

Intel Awards John T. Heron and lab with Outstanding Researcher Award!

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Once a year, Intel presents an award acknowledging work that makes “a significant impact on future technology” and “celebrates exceptional achievements made through Intel sponcered research.” John T. Heron is among the 10 researchers who have recieved this distinguished award.

“The research team demonstrated ultrafast switching of La-doped BiFeO3 ferroelectric capacitors, developed novel metrologies to measure polarization dynamics at nanoscale, demonstrated modeling frameworks to understand the effect of key physical processes such as domain nucleation, growth, and circuit limits on the switching process, and determined a new regime of energy-delay scaling behavior relevant for computing technologies. Furthermore, the researchers developed novel materials critical for accelerating magneto-electric spin-orbit (MESO) device development to deliver target specifications, such as high entropy perovskite oxides with large spin Hall efficiency and resistivity as well as double perovskite ferromagnet layers epitaxially compatible with La-doped BiFeO3.”

Congratulations to both John and the remainder of the research team who supported this achievement! Read more on Intel’s website if you are interested about this achievement.

New Publication! “Engineering antiferromagnetic magnon bands through interlayer spin pumping”

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Abstract: Spin pumping, a central phenomenon in spintronics used to source pure spin currents, is best understood in collinear magnetic multilayers. There is not yet a unified Landau-Lifshitz-Gilbert (LLG) theory that captures the fieldlike and dampinglike torques in a generic noncollinear magnetic multilayer. Here, we theoretically expand the LLG phenomenology to incorporate both dynamic fieldlike and dampinglike torques arising from spin pumping within noncollinear magnetic materials. We find that often overlooked dynamic fieldlike torques are capable of unveiling inversion asymmetries present in magnetic multilayers. Consequently, spin pumping can be used to lift the spectral degeneracy between various magnon modes in noncollinear antiferromagnets. We experimentally confirm this magnon-magnon interaction in a synthetic antiferromagnetic tetralayer, which has highly noncollinear magnetization configurations when under the influence of an external field. Thus, we demonstrate how spin pumping can facilitate a magnon-magnon interaction, significantly expanding how magnonic interactions can be engineered into antiferromagnets and magnetic metamaterials.

Read more at Physics Review Applied

New Publication! “Polydopamine-Assisted Electroless Deposition of Magnetic Functional Coatings for 3D-Printed Microrobots”

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Abstract: Magnetic microrobots are attractive tools for operation in confined spaces due to their small size and untethered wireless operation, particularly in biomedical and environmental applications. Over years of development, many microrobot fabrication methods have been developed; however, they typically require costly specialized physical vapor deposition (PVD) vacuum instrumentation and present homogeneity and conformality coating problems (especially in complex 3D structures). Herein, a solution-based polydopamine (PDA)-assisted electroless deposition method is developed to deposit a superparamagnetic nickel thin film on microrobots. The multilayered functional film design comprises PDA as an adhesive primer and reducing agent, silver nanoclusters as catalysts, and a nickel magnetic top film, all deposited in a batch solution-based process on glass and 3D-printed polymer substrates. This multilayer magnetic coating is implemented and demonstrated in three magnetic microrobot archetypes, including arbitrarily-shaped active particles, microrollers, and helical swimming microrobots, each using distinct actuation working mechanisms. Due to the material-independent interfacial adhesive properties of PDA, this multilayer functionalization strategy can open up new magnetic microrobot fabrication schemes with a broad compatibility with materials and structures (including complex 3D-printed polymer microstructures) and without the need for and limitations of PVD coating approaches.

Read more on Advanced Intelligent Systems

New Publication! “Nernst coefficient of Pt by non-local electrical measurement”

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Abstract: The Nernst effect describes a linear relationship between orthogonal components of a magnetic field, a temperature gradient, and a resulting transverse electric field. A non-local electrical measurement, where injection and detection are physically separated on the specimen, serves as a versatile and effective platform for measuring spin and thermal effects due to the avoided interference with a charge current directly. Here, we quantify the Nernst coefficient of Pt, a common material for spin injection in non-local geometries, by a non-local electrical measurement under modulated temperature and magnetic field and finite element analysis for modeling heat transfer. We determine the Nernst coefficient of Pt from room temperature (8.56 nVK-1 T-1) to 10K (29.3 nVK-1 T-1). Beyond the quantification of the Nernst coefficient, our results show that careful consideration of the thermal properties of the thermal sink and electrode materials is needed when making an interpretation of non-local electrical measurements.

Full text available from Applied Physics Letters

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Our research is at the intersection of multiple disciplines, drawing on principles and methodologies from materials science, chemistry, physics, and electrical engineering. Our mission is to pioneer … Read More

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Ferroelectronics Lab
Address: 2030 H.H. Dow

T: (734) 763-6914
E: jtheron@umich.edu