About

F. Marc Michel is a Professor of Nanoscience at Virginia Tech within the Department of Geosciences. His primary scientific and teaching interests lie at the intersection of mineralogy, environmental science, and nanoscience and technology. His research focuses on understanding how the smallest minerals, such as nanoparticles, are formed, how they react with their surroundings, and how they change over time and space in complex systems and the environment. Michel's work aims to elucidate the structure-property relationships of natural and engineered nanomaterials, decipher the pathways and mechanisms involved in nanoparticle crystallization, and develop methodologies for probing nanoparticle formation in real time. His research employs advanced scattering, spectroscopic, imaging, and computational tools to obtain atomic-scale information, with a particular emphasis on understanding the evolution of nanoparticle structure and properties during crystallization processes. His work is significant for its implications in geological and environmental processes, potential impacts on human and ecosystem health, and applications in energy production, waste disposal, and water treatment. Michel holds a Ph.D. in Geosciences from Stony Brook University and a B.A. in Geology from Colgate University. He teaches courses related to mineralogy and nanoscience, integrating his research on structure-property relationships and advanced analysis methods to prepare students for research in Earth materials and nanotechnology.

Research topics

• Physical chemistry
• Chemistry
• Chemical physics
• Computer Science
• Crystallography
• Nanotechnology
• Materials science
• Biology
• Medicine
• Thermodynamics
• Chromatography
• Organic chemistry
• Statistics
• Quantum mechanics
• Statistical physics
• Nursing
• Composite material
• Mathematics
• Optics
• Mineralogy
• Physics
• Business
• Pathology
• Inorganic chemistry

Selected publications

• Formation and transformation of iron oxy-hydroxide precursor clusters to ferrihydrite

  Environmental Science Nano · 2024-01-01 · 9 citations

  articleOpen accessSenior author

  Rapid precipitation of iron oxy-hydroxide clusters at pH > 4.5 during hydrolysis can lead to the formation of metastable ferrihydrite while their aging at acidic pH (<2.5) forms stable products such as goethite and lepidocrocite.

  PublisherOA PDFDOI

• Goethite and Hematite Nucleation and Growth from Ferrihydrite: Effects of Oxyanion Surface Complexes

  Environmental Science & Technology · 2024-03-20 · 31 citations

  articleOpen accessSenior author

  The presence of oxyanions, such as nitrate (NO3–) and phosphate (PO43–), regulates the nucleation and growth of goethite (Gt) and hematite (Hm) during the transformation of ferrihydrite (Fh). Our previous studies showed that oxyanion surface complexes control the rate and pathway of Fh transformation to Gt and Hm. However, how oxyanion surface complexes control the mechanism of Gt and Hm nucleation and growth during the Fh transformation is still unclear. We used synchrotron scattering methods and cryogenic transmission electron microscopy to investigate the effects of NO3– outer-sphere complexes and PO43– inner-sphere complexes on the mechanism of Gt and Hm formation from Fh. Our TEM results indicated that Gt particles form through a two-step model in which Fh particles first transform to Gt nanoparticles and then crystallographically align and grow to larger particles by oriented attachment (OA). In contrast, for the formation of Hm, imaging shows that Fh particles first aggregate and then transform to Hm through interface nucleation. This is consistent with our X-ray scattering results, which demonstrate that NO3– outer-sphere and PO43– inner-sphere complexes promote the formation of Gt and Hm, respectively. These results have implications for understanding the coupled interactions of oxyanions and iron oxy-hydroxides in Earth-surface environments.

  PublisherOA PDFDOI

• Vertically graded <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Fe</mml:mi></mml:math>-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Ni</mml:mi></mml:math> alloys with low damping and a sizable spin-orbit torque

  Physical Review Applied · 2024-10-21 · 5 citations

  articleOpen access

  In spintronics, conventional devices exploiting spin-orbit torque cannot simultaneously provide both low damping and strong torque, the two necessities for energy-efficient operation. The authors take a different approach to meet both criteria, using Fe-Ni alloy films with steep vertical gradients in composition. Intriguingly, they find that sizable spin-orbit torque emerges even in an alloy without any intentional compositional gradient, due to a gradient in growth-induced strain. Their results give perspective for materials engineering of spin-orbit-torque devices, leveraging asymmetry not only in chemical composition, but also in atomic-scale lattice structure.

  PublisherOA PDFDOI

• Vertically graded FeNi alloys with low damping and a sizeable spin-orbit torque

  2024-10-04 · 1 citations

  article

  Energy-efficient spintronic devices require the following two criteria: (1) a large spin-orbit torque (SOT) and (2) low damping to excite magnetic precession with low current input. Conventional ferromagnet/nonmagnetic-metal bilayers can obtain sizeable SOTs; however, this comes at the expense of drastically increasing the damping. Because the origin or the transmission of spin is interfacial in nature, the ferromagnetic layer must be restricted to ∼1nm in thickness to see substantial SOTs. Here, we present an alternative approach to producing sizeable SOTs that allows for a thicker ferromagnetic layer maintaining low damping. Instead of relying on a single interface, we continuously break the bulk inversion symmetry with a vertical compositional gradient of two ferromagnetic elements: Fe with low intrinsic damping and Ni with sizable spin-orbit coupling. We find low effective damping parameters of <i>&alpha;</i>_eff &lt; 5 &times; 10⁻³ in the FeNi alloy films, despite the steep compositional gradients. Moreover, we reveal a sizable anti-damping SOT efficiency of <i>&theta;</i>_AD &asymp; 0.05, even <i>without</i> an intentional compositional gradient. Through depth-resolved x-ray diffraction, we identify a lattice strain gradient as crucial symmetry breaking that underpins the SOT. Our findings provide fresh insights into damping and SOTs in single-layer ferromagnets for power-efficient spintronic devices.

  PublisherDOI

• Vertically Graded Fe-Ni Alloys with Low Damping and a Sizeable Spin-Orbit Torque

  arXiv (Cornell University) · 2024-06-14

  preprintOpen access

  Energy-efficient spintronic devices require a large spin-orbit torque (SOT) and low damping to excite magnetic precession. In conventional devices with heavy-metal/ferromagnet bilayers, reducing the ferromagnet thickness to $\sim$1 nm enhances the SOT but dramatically increases damping. Here, we investigate an alternative approach based on a 10 nm thick single-layer ferromagnet to attain both low damping and a sizable SOT. Instead of relying on a single interface, we continuously break the bulk inversion symmetry with a vertical compositional gradient of two ferromagnetic elements: Fe with low intrinsic damping and Ni with sizable spin-orbit coupling. We find low effective damping parameters of $α_\mathrm{eff} &lt; 5\times10^{-3}$ in the FeNi alloy films, despite the steep compositional gradients. Moreover, we reveal a sizable anti-damping SOT efficiency of $|θ_\mathrm{DL}| \approx 0.05$, even without an intentional compositional gradient. Through depth-resolved x-ray diffraction, we identify a lattice strain gradient as crucial symmetry breaking that underpins the SOT. Our findings provide fresh insights into damping and SOTs in single-layer ferromagnets for power-efficient spintronic devices.

  PublisherOA PDFDOI

• Geometrically frustrated interactions drive structural complexity in amorphous calcium carbonate

  Nature Chemistry · 2023-09-25 · 40 citations

  articleOpen access

  Abstract Amorphous calcium carbonate is an important precursor for biomineralization in marine organisms. Key outstanding problems include understanding the structure of amorphous calcium carbonate and rationalizing its metastability as an amorphous phase. Here we report high-quality atomistic models of amorphous calcium carbonate generated using state-of-the-art interatomic potentials to help guide fits to X-ray total scattering data. Exploiting a recently developed inversion approach, we extract from these models the effective Ca⋯Ca interaction potential governing the structure. This potential contains minima at two competing distances, corresponding to the two different ways that carbonate ions bridge Ca 2+ -ion pairs. We reveal an unexpected mapping to the Lennard-Jones–Gauss model normally studied in the context of computational soft matter. The empirical model parameters for amorphous calcium carbonate take values known to promote structural complexity. We thus show that both the complex structure and its resilience to crystallization are actually encoded in the geometrically frustrated effective interactions between Ca 2+ ions.

  PublisherOA PDFDOI

• Operando characterization and regulation of metal dissolution and redeposition dynamics near battery electrode surface

  Nature Nanotechnology · 2023 · 123 citations

  • Materials science
  • Chemical physics
  • Chemical engineering
  PublisherOA PDFDOI

• Effects of Oxyanion Surface Loading on the Rate and Pathway of Ferrihydrite Transformation

  ACS Earth and Space Chemistry · 2023-09-26 · 9 citations

  articleOpen accessSenior author

  In natural environments, ferrihydrite (Fh) reacts readily with the contaminant and nutrient oxyanions through surface complexation. While previous experiments showed that the transformation of Fh to Gt and Hm under oxic conditions at 70 °C is controlled by the type and strength of oxyanion surface complexes, the impact of surface loading on this process is only partly understood. Synchrotron scattering methods and chemical analysis were used to develop a kinetic model that describes the impact of oxyanion surface loading on the rate and pathway of Fh transformation by using arsenate (AsO43–) and phosphate (PO43–). Kinetic modeling showed that AsO43– and PO43– adsorption decreased the rate of transformation and favored Hm formation over Gt. Higher surface loadings increasingly inhibited Fh transformation with a greater effect for PO43– compared with AsO43–. This information has implications for understanding the impacts of oxyanions on the transformation of natural Fe to Gt and Hm in environmental systems.

  PublisherOA PDFDOI

• Structural complexity in amorphous calcium carbonate

  Acta Crystallographica Section A Foundations and Advances · 2023-08-22

  article
  PublisherDOI

• Oxyanion Surface Complexes Control the Kinetics and Pathway of Ferrihydrite Transformation to Goethite and Hematite

  Environmental Science & Technology · 2022-10-11 · 61 citations

  articleOpen accessSenior author

  The rate and pathway of ferrihydrite (Fh) transformation at oxic conditions to more stable products is controlled largely by temperature, pH, and the presence of other ions in the system such as nitrate (NO3–), sulfate (SO42–), and arsenate (AsO43–). Although the mechanism of Fh transformation and oxyanion complexation have been separately studied, the effect of surface complex type and strength on the rate and pathway remains only partly understood. We have developed a kinetic model that describes the effects of surface complex type and strength on Fh transformation to goethite (Gt) and hematite (Hm). Two sets of oxyanion-adsorbed Fh samples were prepared, nonbuffered and buffered, aged at 70 ± 1.5 °C, and then characterized using synchrotron X-ray scattering methods and wet chemical analysis. Kinetic modeling showed a significant decrease in the rate of Fh transformation for oxyanion surface complexes dominated by strong inner-sphere (SO42– and AsO43–) versus weak outer-sphere (NO3–) bonding and the control. The results also showed that the Fh transformation pathway is influenced by the type of surface complex such that with increasing strength of bonding, a smaller fraction of Gt forms compared with Hm. These findings are important for understanding and predicting the role of Fh in controlling the transport and fate of metal and metalloid oxyanions in natural and applied systems.

  PublisherOA PDFDOI

Recent grants

• CAREER: Mineral growth by nanoparticle aggregation: Aluminosilicate minerals

  NSF · $560k · 2017–2023

• Mineral Formation by Cluster Self-Assembly: Schwertmannite as a Partially Crystallized Nanomineral

  NSF · $272k · 2015–2018

Frequent coauthors

• John B. Parise

  Stony Brook University

  86 shared

• Gordon E. Brown

  Stanford University

  79 shared

• Gordon E. Brown

  60 shared

• Daniel R. Strongin

  Temple University

  57 shared

• Sytle M. Antao

  University of Calgary

  53 shared

• Lars Ehm

  Stony Brook University

  46 shared

• Clément Levard

  Aix-Marseille Université

  46 shared

• Peter J. Chupas

  Stony Brook University

  42 shared

Labs

• Department of GeosciencesPI

Education

• Postdoctoral Researcher, Geological Sciences

  Stanford University

  2010

• PhD, Geosciences

  Stony Brook University

  2007

• Bachelor of Arts, Geology

  Colgate University

  1998