About

Professor Caroline A. Ross is the Ford Professor of Engineering at MIT's Department of Materials Science and Engineering. She works on magnetic, ferroelectric, and multiferroic materials, primarily oxide thin films, for device applications; magneto-optical films for integrated photonics; and oxide nanocomposites and self-assembly of block copolymers for nanoscale lithography and fabrication. Professor Ross attended Cambridge University in the United Kingdom, where she obtained a BA in 1985 and a PhD in 1988 in materials science, followed by a postdoctoral fellowship at Harvard University. Before joining MIT in 1997, she was an engineer at Komag in Silicon Valley, where she developed hard disk data storage technology. She teaches classes on the structure of materials and magnetic materials. Her research focuses on developing advanced materials for electronic and photonic device applications, with a particular emphasis on oxide-based materials and nanostructures.

Research topics

• Materials science
• Condensed matter physics
• Physics
• Computer Science
• Crystallography
• Geometry
• Classical mechanics
• Mathematics
• Mathematical analysis
• Quantum mechanics
• Optoelectronics
• Optics
• Chemistry
• Nanotechnology
• Theoretical physics

Selected publications

• Field Effects on Magnon‐Induced Domain Wall Motion in a Magnetic Insulator Racetrack

  Advanced Functional Materials · 2026-01-18

  articleSenior author

  ABSTRACT The interactions between magnons and domain walls provide opportunities for extending the functionality of magnonic and spintronic devices. Building on our previous demonstration of field‐free magnon‐induced domain wall motion in low‐damping bismuth‐substituted yttrium iron garnet, this work explores the underlying dynamics and the effects of small magnetic fields on magnon‐driven domain wall motion. Time‐resolved imaging unveils the dynamical response of the garnet track to the RF signal, as well as the excitation of oscillations in a domain wall placed in the track. Magnon transmission is detected over distances of 70 µm from which a damping parameter is extracted. The combined influence of small out‐of‐plane fields (≤ 2 mT) and magnons on domain wall depinning and motion enables direction control. The findings culminate in the demonstration of robust, bidirectional domain wall motion up to 40 µm, establishing a pathway toward field‐tunable, low‐loss magnonic devices.

  PublisherDOI

• Black anatase-TiO2 electrodes for sun-activated photocatalytic degradation of organic water contaminants

  Surfaces and Interfaces · 2025-01-15 · 12 citations

  articleOpen access

  This study presents the synthesis of black anatase in air and its use for the fabrication of a reusable electrode for the photocatalytic degradation of Rhodamine B (RhB) under visible-light. Characterization techniques such as X-ray diffraction, Raman spectroscopy, and Transmission Electron Microscopy (TEM) were used to analyze the properties of black anatase. The immobilization of black TiO 2 on a glass substrate eliminates the need for post-treatment recovery of the photocatalyst. Enhancement of photocatalytic activity was achieved by depositing a 4 nm platinum layer on the black anatase TiO 2 electrode. Activation of the photocatalytic process (λ ≥ 400 nm) was conducted with a solar simulator, and the degradation of RhB was monitored through visible absorption and time-resolved fluorescence spectroscopy, revealing degradation efficiencies of 94 % and 89 % after 40 and 60 min, respectively. These results are attributed to the elevated levels of oxygen vacancies and the Schottky barrier formed between the platinum layer and black anatase. The methodology's simplicity and the significant photocatalytic efficiency suggest potential for widespread application in solar-driven photocatalytic degradation.

  PublisherDOI

• Integrated magneto-optic based magnetometer: classical and quantum limits

  2025-09-08

  articleOpen access

  Magnetic field sensors with high sensitivity and spatial resolution have profoundly impacted diverse applications ranging from geo-positioning and navigation to medical imaging, materials science, and space exploration. However, the use of high-precision magnetometers is often limited due to their bulky size or low energy efficiency. In this work, we present the design, modeling and an experimental demonstration of an all-optical magnetometer based on silicon integrated photonics heterogeneously integrated with a magneto-optic thin film. By bonding a thin cerium-yttrium iron garnet layer onto an integrated silicon photonic interferometer, small magnetic field fluctuations can be detected through the non-reciprocal phase shift in the sensor. This strategy enables more than 80 dB of dynamic range with better than 40~pT/Hz^1/2 sensitivity at room temperature. Importantly, by leveraging silicon photonics, the core platform is scalable through foundry manufacturing, and the ultra-low power requirements enable complete system integration with on-chip lasers, detectors, and quantum elements for enhanced sensitivity. This work provides a path to realizing a compact, scalable, room temperature magnetometer based on integrated photonic systems, opening new opportunities for ultra-sensitive and ultra-efficient magnetic field detectors.

  PublisherDOI

• Electrically-driven nonreciprocal silicon photonic isolator based on monolithically integrated bismuth terbium iron garnet

  2025-05-26

  preprint

  Photonic isolation is an essential on-chip function needed to stabilize laser operation and prevent cross-talk between different components within a communication system. Monolithically integrated isolator designs incorporate magnetooptical cladding consisting of doped yttrium iron garnet (YIG), such as Ce:YIG and Bi:YIG, where a YIG seedlayer is required prior to the deposition and subsequent crystallization of doped YIG. This adversely impacts isolator performance through reduced mode overlap with the doped YIG layer. Furthermore, the Faraday rotations of YIG and Ce-doped YIG have opposing signs such that they partially cancel out. This work demonstrates a seedlayer-free, monolithic nonreciprocal photonic platform based on an alternative garnet formulation, bismuth doped terbium iron garnet (Bi:TbIG). We further realize on-chip integration of electromagnets to obviate the requirements of external magnets. An isolator based on the Mach-Zehnder interferometer (MZI) architecture is implemented, which records π nonreciprocal phase shift with a driving current of 114 mA. Optical isolation as high as 24 dB is achieved.

  PublisherDOI

• Néel domain walls with bistable chirality in a perpendicularly magnetized ferrimagnetic insulator

  Nature Communications · 2025-06-04 · 1 citations

  articleOpen access

  Field-free spin-orbit torque-driven domain wall motion in magnetic thin films with perpendicular magnetic anisotropy (PMA) requires the domain walls to have Néel character. Conventionally, Néel domain walls are stabilized by the Dzyaloshinskii-Moriya interaction (DMI) in ultrathin films. Here, in a europium iron garnet thin film with PMA and an additional uniaxial in-plane anisotropy, we demonstrate two bistable Néel domain wall states in the absence of DMI, and the capability to toggle the wall states with an in-plane field pulse and consequently their directions of motion under a current pulse. We present a phase diagram for the bistable Néel domain wall states as a function of in-plane field pulse width and amplitude. By fitting the experimental data to an analytical model of Néel wall reversal through the nucleation and propagation of Bloch lines, we extract the length of the initial reversed domain wall segment and Bloch line nucleation energy barrier. Current-driven motion of in-plane anisotropy stabilized Néel walls is qualitatively different from that of DMI-stabilized ones owing to the different symmetry of the effective fields that stabilize the Néel configuration. Furthermore, we present a proof of principle demonstration for 2-bit random number generation based on the stochastic reversal of domain wall chirality. These results provide critical insight into the topological energy barrier of Bloch lines and identify paths towards domain wall-based memory and computing devices. Neel domain walls are typically stabilized by an interfacial Dzyaloshinskii-Moriya interaction, with a chirality that is fixed by the sample materials. Here, Song, Huang and coauthors demonstrate the existence of two bistable Néel domain wall states with opposite chiralities, and the switching between these via magnetic field pulses

  PublisherOA PDFDOI

• Strain Mediated Voltage Control of Magnetic Anisotropy and Magnetization Reversal in Bismuth-Substituted Yttrium Iron Garnet Films and Mesostructures

  ACS Applied Materials & Interfaces · 2025-11-21 · 1 citations

  articleOpen access

  We report on magnetic anisotropy modulation in Bismuth-substituted Yttrium Iron Garnet (Bi-YIG) thin films and mesoscale patterned structures deposited on a PMN–PT substrate with the application of a voltage-induced strain. The Bi content is selected for low coercivity and higher magnetostriction than that of YIG, yielding significant changes in the hysteresis loops through the magnetoelastic effect. The piezoelectric substrate is poled along its thickness, which is the [011] direction, by applying a voltage across the PMN–PT/SiO2/Bi-YIG/Pt heterostructure. In situ magneto-optical Kerr effect microscopy (MOKE) shows the modulation of magnetic anisotropy with voltage-induced strain. Furthermore, voltage control of the magnetic domain state of the Bi-YIG film at a fixed magnetic field produces 90° switching of the magnetization easy axis above a threshold voltage. The magnetoelectric coefficient of the heterostructure is 1.05 × 10–7 s m–1 which is competitive with that of other ferromagnetic oxide films on ferroelectric substrates such as La0.67Sr0.33MnO3/PMN–PT and YIG/PMN–PZT. Voltage control of magnetization reversal fields in 5–30 μm wide dots and racetracks of Bi-YIG show potential for energy-efficient nonvolatile memory and neuromorphic computing devices.

  PublisherDOI

• Electrically-driven nonreciprocal silicon photonic isolator based on monolithically integrated bismuth terbium iron garnet

  2025-05-26

  preprint

  Photonic isolation is an essential on-chip function needed to stabilize laser operation and prevent cross-talk between different components within a communication system. Monolithically integrated isolator designs incorporate magnetooptical cladding consisting of doped yttrium iron garnet (YIG), such as Ce:YIG and Bi:YIG, where a YIG seedlayer is required prior to the deposition and subsequent crystallization of doped YIG. This adversely impacts isolator performance through reduced mode overlap with the doped YIG layer. Furthermore, the Faraday rotations of YIG and Ce-doped YIG have opposing signs such that they partially cancel out. This work demonstrates a seedlayer-free, monolithic nonreciprocal photonic platform based on an alternative garnet formulation, bismuth doped terbium iron garnet (Bi:TbIG). We further realize on-chip integration of electromagnets to obviate the requirements of external magnets. An isolator based on the Mach-Zehnder interferometer (MZI) architecture is implemented, which records π nonreciprocal phase shift with a driving current of 114 mA. Optical isolation as high as 24 dB is achieved.

  PublisherDOI

• ROMP of Macromonomers Prepared by ROMP: Expanding Access to Complex, Functional Bottlebrush Polymers

  Journal of the American Chemical Society · 2025-01-14 · 9 citations

  articleCorresponding

  Graft-through ring-opening metathesis polymerization (ROMP) of norbornene-terminated macromonomers (MMs) prepared using various polymerization methods has been extensively used for the synthesis of bottlebrush (co)polymers, yet the potential of ROMP for the synthesis of MMs that can subsequently be polymerized by graft-through ROMP to produce new bottlebrush compositions remains untapped. Here, we report an efficient "ROMP-of-ROMP" method that involves the synthesis of norbornene-terminated poly(norbornene imide) (PNI)-based MMs that, following ROMP, provide new families of bottlebrush (co)polymers and "brush-on-brush" hierarchical architectures. In the bulk state, the organization of the PNI pendants drives bottlebrush backbone extension to enable rapid assembly of asymmetric lamellar morphologies with large asymmetry factors. Overall, this work expands the scope of complex macromolecular architectures and provides insights into the interplay of backbone rigidity and self-assembly that will guide future nanolithography applications.

  PublisherDOI

• Room-temperature laser crystallization of oxygen vacancy-engineered zirconia for additive manufacturing

  Additive manufacturing · 2025-08-01 · 1 citations

  articleOpen access

  We demonstrate how strategically engineered oxygen vacancies enable room-temperature laser crystallization of zirconia (ZrO₂) in ambient air. Our sol-gel chelation synthesis creates amorphous ZrO₂ nanoparticles with a high concentration of oxygen vacancies that fundamentally alter the material's energy landscape. These defects create sub-bandgap states that facilitate visible light absorption and dramatically reduce the energy barrier for crystallization. Under low-energy laser irradiation (405-532 nm), oxygen vacancies mediate a rapid phase transformation mechanism where atmospheric oxygen interacts with vacancy sites, triggering ionic rearrangement and crystallization without conventional high-temperature processing. For comparison purposes, this study also explores the thermal crystallization of black zirconia in an oxidative atmosphere, a process typically performed under vacuum or inert conditions. Through comprehensive characterization (FTIR, EPR, XPS, XRD, Raman), we establish that vacancy-mediated crystallization produces monoclinic ZrO₂ with preserved defect structures, yielding a distinctive black phase with 25.6% oxygen vacancy concentration, significantly higher than thermally processed counterparts (9.2%). This vacancy-enabled crystallization circumvents the need for extreme temperatures (>1170°C) typically required for ZrO₂ processing, making it compatible with additive manufacturing. Using a modified 3D printer with a 405 nm laser, we demonstrate patterned crystallization of complex architectures, opening new possibilities for fabricating advanced ZrO₂-based devices for photocatalysis, fuel cells, and energy applications. This work provides fundamental insights into defect-mediated phase transformations and establishes a new paradigm for room-temperature ceramic processing.

  PublisherDOI

• Directed self-assembly of 3D interconnected networks

  Science Advances · 2025-11-19 · 1 citations

  articleOpen accessSenior authorCorresponding

  Directed self-assembly (DSA) of block copolymers (BCPs) has long been included in the semiconductor roadmap as a lithographic pathway to enable continued device scaling. Tremendous progress has been made in generating two-dimensional (2D) BCP patterns with device-relevant features and low defect density and in transferring these patterns to functional materials. Extension of pattern generation into 3D could markedly enhance the utility of BCPs in nanoscale manufacturing, but methods to template and synthesize well-ordered, nontrivial 3D structures are less well developed. Here, we demonstrate a hierarchical DSA method to generate cross-point structures with connected in-plane and out-of-plane segments and controlled orientation angle between the horizontal layers. Various highly ordered, 3D interconnected networks, including ladder and cross-point structures, are produced by combinations of surface modification, BCP periodicity, and topographic templates, expanding the capabilities of BCP-derived nanofabrication.

  PublisherDOI

Recent grants

• Epitaxial Ceramic Nanocomposites by Design

  NSF · $500k · 2019–2023

• GOALI: Magnetooptical Materials for Integrated Optical Isolators

  NSF · $349k · 2006–2011

• Ferromagnetic Magnetooptical Oxides for Nonreciprocal Photonic Devices

  NSF · $652k · 2011–2015

• PIC: CMOS-compatible, monolithic, and high-performance optical isolators on silicon

  NSF · $500k · 2020–2023

• Materials World Network: Triblock Terpolymers for Self-Assembled Nanolithography

  NSF · $360k · 2010–2014

Frequent coauthors

• Takian Fakhrul

  Massachusetts Institute of Technology

  40 shared

• Alfredo Alexander‐Katz

  Massachusetts Institute of Technology

  40 shared

• Yan Zhang

  34 shared

• Mehmet C. Onbaşlı

  Koç University

  33 shared

• Shuai Ning

  Kunming University of Science and Technology

  33 shared

• Lukáš Beran

  32 shared

• Geoffrey S. D. Beach

  Massachusetts Institute of Technology

  29 shared

• Dong Hun Kim

  Purdue University West Lafayette

  28 shared

Labs

• The Ross GroupPI

Education

• Ph.D., Materials Science and Engineering

  Massachusetts Institute of Technology

  2005

• M.S., Materials Science and Engineering

  Massachusetts Institute of Technology

  2001

• B.S., Materials Science and Engineering

  Massachusetts Institute of Technology

  1999

Awards & honors

• 2013 Fellow, Institute of Electrical and Electronics Enginee…
• 2009 Fellow, Materials Research Society
• 2004 Irwin Sizer Award for the Most Significant Improvement…
• 2004 Fellow, American Physical Society
• 2000 Joseph Lane Award for Excellence in Teaching