A New Kind of Computer

Over the years, computers have been getting smaller in size and faster in speed. Almost all computers and electronics around us are based on millions of transistors. A transistor is a device to control the flow of electric charge in a circuit. The scaling of computers (getting smaller in size and faster in speed) is directly related to the miniaturization of transistors on a silicon chip. However, quantum mechanics physically limits this reduction in size, and therefore alternatives to electronics and conventional computing are sought.

One attractive candidate is spintronics, which exploits the spin in addition to the charge of the electron for information processing, transport and storage. Learn about spintronics research in Oxford here.

Since its emergence, spintronics has progressed into many sub-disciplines and has already delivered great impact as well. For example, spintronic magnetic field sensors gave birth to the modern magnetic storage discs and played an essential role in pushing forward the information age. However, even spintronics based on the electron as the messenger of information has not been able to elude certain challenges, like the Joule heating loss.

Hence, a wave-based paradigm called magnonics becomes very relevant. It revolves around the study of generation, manipulation and detection of spin waves, which are essentially propagating excitations in the magnetization of an electrically insulating material. Learn about magnonics research in Oxford here.

Unlike spintronics, magnonics makes use of only the spin wave excitations in
magnetic materials. In other words, on the one hand, spintronics makes use of moving
electrons but confines these currents to comprise either spin-up or spin-down electrons (which constitutes an additional degree of freedom for information processing). On the other hand, magnonics work without propagating electrons and rely solely on the movement of magnons, the particle-like units of spin waves, as information carriers in a magnetic material.

Areas of physics and engineering research based on the kind of information carrier and motion involved.

In magnonic systems, heat losses are significantly reduced because of the absence of moving charge carriers in the magnonic circuits. Additionally, spin waves have the ability to support wavelengths and frequencies in the nanometer and gigahertz regime, respectively, allowing device miniaturization and increased clock frequencies. Moreover, magnons can propagate at appreciable speeds over distances up to about a centimeter without serious heat dissipation in certain materials, a feat not possible for electrons.

Notable examples of state-of-the-art spin-wave or magnon computing technology are the spin-wave transistor and spin-wave logic gates.

A spin-wave transistor: Signal in Gate antenna controls spin-wave transmission from Source antenna to Drain antenna. The medium of propagation is a YIG waveguide. YIG stands for yttrium iron garnet, which is a magnetic insulator.
A spin-wave logic gate: The device is made of two waveguides in which spin waves propagate. The microwave signals are split at the source and combined at the output. A logic gate performs a mathematical operation and is the basic building block of any computer.

Hence, spin-wave systems have the potential to catalyse the development of new technologies such as more efficient computers and whole new platforms for computing.