Spin Wave Computing

transistor – a device to control the flow of electric charge in a
circuit. Miniaturization of transistors on an integrated circuit chip means faster
electronics. However, quantum mechanics physically limits this reduction in size. As the
Moore’s law curve continues to saturate, alternatives towards relatively more efficientthan-present electronics and 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. Since its emergence,
this field 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
Research Motivation Statement Muhammad Hamza Waseem
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. 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. This capacity renders some desirable characteristics to magnonic
systems. To exemplify, Ohmic losses can be 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.