Semiconductor Shows Ferromagnetism At Room Temperature

Researchers have reported growing iron-doped ferromagnetic semiconductors that work at room temperature—a longstanding physical constraint.

AsianScientist (May 17, 2016) – More, faster, better, cheaper—these are the demands of our device-happy and data-centered world. Meeting these demands requires technologies for processing and storing information. Now, reseearchers in Japan and Vietnam appear to have overcome a significant obstacle to the development of next-generation device technologies.

Specializing in the emerging field of semiconductor spintronics, the team from the University of Tokyo, Tokyo Institute of Technology and Ho Chi Minh University of Pedagogy have become the first to report growing iron-doped ferromagnetic semiconductors working at room temperature—a longstanding physical constraint. Their work has been published in Applied Physics Letters.

Doping is the practice of adding atoms of impurities to a semiconductor lattice to modify electrical structure and properties. Ferromagnetic semiconductors are valued for their potential to enhance device functionality by utilizing the spin degrees of freedom of electrons in semiconductor devices.

“Bridging semiconductors and magnetism is desirable because it would provide new opportunities of utilizing spin degrees of freedom in semiconductor devices,” explained research leader Dr. Masaaki Tanaka from the Department of Electrical Engineering & Information Systems, University of Tokyo.

“Our approach is, in fact, against the traditional views of material design for ferromagnetic semiconductors. In our work, we have made a breakthrough by growing an iron-doped semiconductor which shows ferromagnetism up to room temperature for the first time in semiconductors that have good compatibility with modern electronics.”

Tanaka added that their work opens up ways to realize semiconductor spintronic devices operating at room temperature.

The researchers’ work challenges the prevailing theory that predicted a type of semiconductor known as ‘wide band gap’ would be strongly ferromagnetic. Most research focuses on the wide band gap approach.

“We instead chose narrow-gap semiconductors, such as indium arsenide, or gallium antimonide, as the host semiconductors,” Tanaka said.

This choice enabled them to obtain ferromagnetism and conserve it at room temperature by adjusting doping concentrations.

Investigators have long envisioned bridging semiconductors and magnetism to create new opportunities of utilizing spin degrees of freedom and harnessing electron spin in semiconductors. But until now, ferromagnetic semiconductors have only worked under experimental conditions at extremely low, cold temperatures, typically lower than 200 Kelvin (K) or -73 degrees Celsius (°C), which is much colder than the freezing point of water, 273.15 K.

Potential applications of ferromagnetic-semiconductors include designing new and improved devices, such as spin transistors.

“Spin transistors are expected to be used as the basic element of low-power-consumption, non-volatile and reconfigurable logic circuits,” Tanaka explained.

On a practical level, the team continues its research with the goal of applying iron-doped ferromagnetic semiconductors to the field of spintronic device innovation. On a theoretical level, the team is interested in re-evaluating conventional theories of magnetism in semiconductors.

“Based on the results of many experimental tests, we have proven that ferromagnetism in our iron-doped semiconductor is intrinsic,” Tanaka said.

The article can be found at: Nguyen et al. (2016) High-temperature Ferromagnetism in Heavily Fe-Doped Ferromagnetic Semiconductor (Ga,Fe)Sb.


Source: American Institute of Physics.
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