Transistors are the essential building blocks of modern electronics, powering everything from smartphones to supercomputers. Traditionally made of silicon, these devices regulate electrical current or amplify weak signals. But silicon has physical limits: it cannot operate below a certain voltage, restricting how compact and energy-efficient future electronics can become.
MIT engineers have now introduced a breakthrough alternative. By replacing silicon with a magnetic semiconductor, they developed a magnetic transistor that not only switches current far more strongly than previous designs but also stores information. This dual capability could lead to smaller, faster, and more efficient electronics.
Harnessing the power of magnetism
The innovation builds on the field of spintronics, which uses the spin of electrons in addition to their charge. Electron spin, a fundamental property that makes electrons behave like tiny magnets, has long promised new ways to control electricity.
Until now, researchers struggled because most magnetic materials lacked the right electronic properties to rival silicon. “In this work, we combine magnetism and semiconductor physics to realize useful spintronic devices,” said Luqiao Liu, an associate professor in MIT’s Department of Electrical Engineering and Computer Science (eecs).
The team turned to chromium sulfur bromide, a two-dimensional material that acts as a magnetic semiconductor. Its structure allows researchers to switch cleanly between two magnetic states, making it ideal for smooth transistor operation. Crucially, unlike many other 2d materials, it remains stable in air.
“One of the biggest challenges we faced was finding the right material. We tried many other materials that didn’t work,” explained graduate student Chung-tao Chou, co-lead author of the study.
A cleaner process with fewer defects
The researchers didn’t just find the right material; they also improved how it’s used. They optimized the process to reduce defects in the magnetic film, further boosting the transistor’s performance.
To fabricate the device, engineers patterned electrodes on a silicon substrate and transferred the thin magnetic material on top. Instead of solvents or glue—which often contaminate surfaces—they used a simple tape method to pick up and place the material.
“A lot of researchers will use solvents or glue to do the transfer, but transistors require a very clean surface. We eliminate all those risks by simplifying this step,” Chou said.
This cleaner method gave their transistor a sharp advantage. While most magnetic transistors shift current by only a few percent, the MIT device changes it by a factor of ten. That stronger switching allows faster, more reliable readouts.
Switching with less energy
Initially, the transistor’s magnetic states were toggled using an external magnetic field. Even then, it consumed far less energy than a typical silicon transistor. More importantly, the researchers showed that electrical currents can also control the magnetic states.
This step is critical for real-world applications. Engineers cannot rely on external magnets for billions of transistors on a single chip. Electrical control ensures scalability, making it possible to integrate the device into practical circuits.
Logic and memory combined
The new transistor doesn’t just regulate current—it also remembers. Conventional memory devices use separate magnetic cells to store data and transistors to read it. By merging both functions, the MIT design simplifies circuit architecture.
“Now, not only are transistors turning on and off, they are also remembering information. And because we can switch the transistor with greater magnitude, the signal is much stronger so we can read out the information faster, and in a much more reliable way,” Liu said.
This innovation could unlock new possibilities for high-performance electronics, where speed, compactness, and reliability are crucial.
Collaboration across disciplines
The project was highly collaborative, drawing expertise from multiple departments. In addition to Liu and Chou, the research team included co-lead author Eugene Park, graduate student in the Department of Materials Science and Engineering (dmse); Julian Klein, a dmse research scientist; Josep Ingla-Aynes, postdoc at the Plasma Science and Fusion Center; Jagadeesh S. Moodera, senior research scientist in physics; Frances Ross, tdk Professor in dmse; and collaborators from the University of Chemistry and Technology in Prague.
Their findings were published in Physical Review Letters, a leading journal in physics research.
Overcoming silicon’s ceiling
For decades, engineers have pushed silicon transistors to their physical limits. They act like tiny switches that turn circuits on and off using small voltages, but they cannot function below a certain energy threshold. This ceiling blocks progress in efficiency and compactness.
Magnetic semiconductors offer a way forward. By directly linking magnetism to electronic behavior, they enable transistors to operate with far less energy while opening new design opportunities.
“People have known about magnets for thousands of years, but there are very limited ways to incorporate magnetism into electronics. We have shown a new way to efficiently utilize magnetism that opens up a lot of possibilities for future applications and research,” Chou emphasized.
Looking ahead
The MIT team is now exploring how to scale up their method to fabricate arrays of transistors and refine the use of electrical currents for control. This will be essential for integrating the technology into next-generation chips.
The research was supported by the Semiconductor Research Corporation, the U.S. Defense Advanced Research Projects Agency (darpa), the National Science Foundation (nsf), the Department of Energy (doe), the U.S. Army Research Office, the Czech Ministry of Education, Youth, and Sports, and was partially carried out at mit.nano facilities.
By merging magnetism and electronics in a new way, MIT engineers have opened a promising pathway beyond silicon. If further developed, magnetic transistors with built-in memory could transform how circuits are designed—leading to smaller, faster, and more energy-efficient electronics for the future.
Source: Physical Review Letters
