Tuning Magnetism with Voltage Opens New Path to Neuromorphic Circuits
Yayoi Takamura, a professor and chair of the Department of Materials Science and Engineering at the University of California, Davis, and her group are part of a collaborative team that has demonstrated a new way to control the magnetic behavior of quantum materials using applied voltages.
Lanthanum strontium manganite, or LSMO, is a quantum material that has a strong link between its magnetic and electrical properties: it is magnetic and conducts electricity at low temperatures, but it is nonmagnetic and an insulator at room temperature.
Takamura and her group have worked with LSMO extensively over the years. They provided the samples and knowledge of the material properties required to properly interpret the data and ensure the measurements could be performed safely and without introducing artifacts.
The team discovered that a sufficiently large voltage applied to LSMO when it is patterned down to microscale and nanoscale dimensions causes the material to split into regions with distinct magnetic and electrical properties. The profile of magnetic/conducting and non-magnetic/insulating regions results in a unique electrical phenomenon referred to as negative differential resistance.
Normally magnetic properties of materials do not respond readily to applied voltages. However, in LSMO, an applied voltage can be used to tune different magnetic/electrical regions in the same material.
This breakthrough could lead to energy-efficient methods for controlling magnetism in next-generation spintronic computing devices, which store and process information, and neuromorphic computing devices, which use specialized hardware to mimic brain-like processing for more efficient AI.
The experiments with LSMO, which resulted in the paper Electrical Control of Magnetic Resonance in Phase Change Materials, involved Takamura and her group from UC Davis, as well as researchers from UC San Diego, New York University, and the University of Denver, and the Advanced Light Source, or ALS, at Lawrence Berkeley National Laboratory.
Takamura and her group worked closely with the paper’s lead author, Tian-Yue Chen, a postdoctoral researcher at New York University, to conduct the X-ray photoemission electron microscopy, or X-PEEM, performed at ALS to image the magnetic domains of LSMO with sub-micron spatial resolution and how they are impacted by the applied voltage. Not only was Takamura’s team heavily involved in growing the LSMO thin film and acquiring the X-PEEM images, but also in the interpretation of the images and writing of the manuscript.
This work is part of a long series of publications that have resulted from a Department of Energy Energy Frontier Research Center called Quantum Materials for Energy Efficient Neuromorphic Computing, or Q-MEEN-C.
“The most exciting part of working with Q-MEEN-C is working with a team of researchers with distinct and complementary expertise,” Takamura said. “It is through that combination that we were able to be successful with the design of the sample needed to perform the experiments at the ALS as well as the execution of the measurements. These were tricky measurements that not many people have attempted, so it was a learning experience about what can and cannot be performed in the microscope.”
