New materials put spin into spintronics

Researchers in the US have created semiconducting materials that exhibit the key properties essential to the development of semiconductor spintronic devices.

A team of researchers led by University at Buffalo physicists have reported that they have created semiconducting materials that exhibit the key properties essential to the development of semiconductor spintronic devices.

The research reportedly demonstrates that development of new semiconductor spintronic devices, including a prototype magnetic semiconductor, is not very far off, according to the UB physicists.

Spintronics, the emerging field of technology in which not just the charge, but the spin, of electrons is exploited, is expected to lead to dramatic improvements in electronic systems and devices such as memory elements, logic elements, spin transistors and spin valves.

If certain classes of spintronic devices become a reality, they will outperform conventional electronic devices because instead of relying on one of two binary digits to encode information, they could process data using any of an infinite variety of spin states of electrons.

The UB materials are digital alloys in which Gallium Antimonide/Manganese is layered in very thin slices, measuring just a few atoms, with some of the layers containing controlled mixtures of the two.

These digital alloys are said to take just a few hours to fabricate using a technique called molecular beam epitaxy, in which an ultra-high-vacuum environment creates new combinations of atoms, which don’t exist in nature.

Because the material developed at UB, Gallium Antimonide/Manganese (GaSb/Mn), is a modification of a well-studied semiconducting material, it should be comparatively easy to integrate with existing electronic systems, an important advantage.

The semiconductors developed at UB are reportedly the first to demonstrate hysteresis at room temperature, which the researchers say is an unambiguous signature of ferromagnetism, another prerequisite for some types of spintronic devices, in which a lasting magnetic effect does not disappear when an applied magnetic field is withdrawn.

For most practical applications, the physicists explained, functionality at room temperature and even higher temperatures is critical.

The Gallium Antimonide/Manganese showed ferromagnetism up to 400 Kelvin (about 260-degrees Fahrenheit), which is the upper limit of the magnetometer, so the physicists expect to see the phenomena at even higher temperatures.

By modifying their semiconductor and combining it with a non-magnetic semiconductor in a heterostructure, a type of structure in which two semiconductors are sandwiched together, the UB team expects to be able to manipulate spin-polarised electrons, an important goal of creating materials with spintronic properties.

‘Based on the new functionalities associated with this ‘spin degree of freedom,’ there are entirely new circuit possibilities which have not even been envisioned yet,’ said Bruce McCombe, Ph.D., SUNY Distinguished Professor in the UB Department of Physics, and associate dean of the UB College of Arts and Sciences.