Frances HELLOGO.GIFellman Group

Amorphous and nanostructured Silicon
Fe/Cr Multilayers
Magnetic Oxides
Magnetic semiconductors
Magnetic Molecules

Our group studies thermodynamic and temperature-dependent properties of materials.

We 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 us 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.

We 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. Our 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.

We 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.

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

Here you can download posters showing the direction of our magnetic research (
PDF), and with heat capacity measurements (PDF). For a detailed description of our research, take a look to the specific projects.