By Emily Hubbell

Dr. Jadwisienczak poses in his lab. He recently received funding for a new MOKE spectrograph.

When Wojciech Jadwisienczak pulled an old magnetic characterization system out from the corner of his lab two years ago, he knew the equipment was outdated. For starters, the heart of the system—its electromagnet—was more than 40 years old.

“New equipment for magnetic characterization is badly needed at OU,” said Jadwisienczak, assistant professor of electrical engineering. “We have limited capability to characterize magnetic materials at the micro or nano scale after they are taken out of the growth chamber.”

Jadwisienczak was recently awarded a DURIP grant from the Army Research Office to develop the magneto-optical Kerr effect (MOKE) spectrograph, a modular magnetic characterization system.

Although scientists have been studying magnetism for centuries, the research field is constantly yielding new materials with optimized magnetic properties suitable for novel devices. The MOKE spectrograph will help foster magnetic ex situ research — research that focuses on the properties of materials after their growth — on campus.

The MOKE spectrograph’s most important—and most expensive—component is its electromagnet, which generates a magnetic field when a current passes through its coils. The researchers place a material that needs to be characterized into this magnetic field and probe it with polarized light, typically a laser beam. When this light reflects off the material, researchers can analyze the changes of polarization in the reflected beam and can then determine what characteristics in the material caused these changes.

Using the noninvasive light beam as a probe gives the system flexibility, allowing researchers to perform experiments in different configurations and for samples with different crystallographical orientations.  The spectrograph will be capable of performing measurements in three geometries—polar, longitudal and transversal—and in a spectral range spanning from ultraviolet to near infrared.

The equipment will also be capable of operating at low temperatures. A special nonmagnetic cryogenics system will allow researchers to investigate materials with magnetic properties barely observable at room temperature without interfering with measurements.

Currently, OU researchers who grow magnetic materials send the samples to other universities for characterization. The new equipment will help meet the demand for magnetic characterization on campus, Jadwisienczak said.

“There is a loophole at OU. Unless we have collaboration between the people growing the material and the people characterizing the material, we cannot close that loophole,” he said.

He added that any researchers working with thin films or materials with magnetic properties will find the MOKE spectrograph useful. In the future, Jadwisienczak plans to adapt the MOKE system for use with low dimensional magnetic materials such as quantum dots.

The new system, called Nano-MOKE, will open up a new avenue for the post-growth magneto-optical characterization of these materials at OU, he said.