Frances Hellman

Research Expertise and Interest

condensed matter physics and materials science

Research Description

The Frances Hellman research group studies thermodynamic and temperature-dependent properties of materials.

They have developed a series of experiments based on MEMS "lab-on-a-chip" devices utilizing a silicon nitride membrane as a thermal isolation platform which allows them to study orders of magnitude smaller sample sizes than other available thermodynamic measurements such as thin films (as thin as 20nm), nanoparticles, and tiny crystals. Experiments include heat capacity measurements, thermal conductivity and thermopower measurements.

They have modified this membrane-based device into a portable heater stage that is transparent to x-rays for use in in-situ temperature-dependent measurements in facilities that do not support macroscale heating such as sensitive x-ray beamlines at synchrotrons. Their latest development of the device consists in adding a thin biaxially oriented MgO layer for epitaxial growth of thin films on the amorphous silicon nitride membrane.

They study a wide range of materials; current projects include ferromagnetic and antiferromagnetic thin films and nanoparticles, studying the effects of disorder on the magnetic, transport, and thermodynamic properties of magnetic materials and relaxor ferroelectrics, and low temperature thermal properties of amorphous materials.

They currently have openings for graduate students in a variety of projects, including studying the thermodynamics of magnetocaloric materials, multilayer systems, semiconductor nanowires, and various magnetic materials.

For a detailed description of their research including the direction of their magnetic research and their work with heat capacity measurements, visit their group website.

Featured in the Media

Please note: The views and opinions expressed in these articles are those of the authors and do not necessarily reflect the official policy or positions of UC Berkeley.
April 6, 2020

The Search for the Perfect Mirror

The Atlantic
Natalie Wolchover and Quanta
Physics professor Frances Hellman is profiled here for her work with a 1,000-person team to find something close to an "ideal glass" for the Laser Interferometer Gravitational-Wave Observatory, or LIGO. The observatory uses pure glass mirrors to detect gravitational waves that flutter past Earth, altering space-time. "LIGO at this point is literally limited by" flaws in the glass they're using, Professor Hellman says. Despite the detectors' "astonishing vibration isolation, damping, all kinds of stuff that has led to the extraordinary sensitivity," she says, "the one thing they haven't been able to get rid of are these funny little atomic motions in the mirror coatings."
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July 19, 2019

This New Liquid Is Magnetic, and Mesmerizing

New York Times
Knvul Sheikh
A team of scientists, including researchers at Berkeley and the Lawrence Berkeley National Laboratory, has co-created a new magnetic material that is liquid and can change shape. It was accomplished using a special 3D printer to inject iron oxide nanoparticles into millimeter-scale droplets of toluene. The researchers believe the liquid magnets would be helpful in delivering drugs to specific locations in the body, and to create "soft robots." But that's just a start. As lead author Thomas Russell, a polymer scientist at the University of Massachusetts, Amherst, says: "We hope these findings will enable people to step back and think of new applications for liquid magnets. ... Because until now, people in material sciences haven't thought this was possible at all." Berkeley co-authors include physics professor Frances Hellman; Alejandro Ceballos, a doctoral alum from the Hellman lab, now a postdoc at the Lawrence Livermore National Laboratory; and graduate materials science and engineering student Yufeng Jiang.
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