Nanomagnets Challenge Semiconductor Transistors
Shamita Chakraborty · Zenodo (CERN European Organization for Nuclear Research) · 2016
That the magnetic orientation of ferromagnets can be changed using magnetic fields has been known for centuries. But the exploration of magnetization control without any additional magnetic field has only just begun. Ever since William Gilbert's sixteenth century treatise De Magnete, it has been known that magnetic fields can be used to manipulate the magnetic orientation of ferromagnets. This has been the foundation for electronic applications of magnetic materials for the past 100 years, in the form of, for example, inductors, microwave isolators and magnetic disk drives. A nanomagnet is a submicrometric system that presents spontaneous magnetic order (magnetization) at zero applied magnetic field (remanence). Researchers at the Technische Universität München (TUM) have demonstrated a new kind of building block for digital integrated circuits which uses 3D arrangements of nano-scale magnets instead of transistors. In a 3D stack of nanomagnets, the researchers have implemented a so-called majority logic gate, which could serve as a programmable switch in a digital circuit. A reversal of polarity represents a switch between Boolean logic states. The state of the device is determined by three input magnets, one of which sits 60nm below the other two, and is read out by a single output magnet. Magnetic circuits are non-volatile, have extremely low energy consumption and can operate at room temperature and resist radiation. They can allow very dense packing. The most basic building blocks, the individual nanomagnets, are comparable in size to individual transistors. Furthermore, where transistors require contacts and wiring, nanomagnets operate purely with coupling fields. Also, in building CMOS and nanomagnetic devices that have the same function – for example, a so-called full-adder – it can take fewer magnets than transistors to get the job done. Finally, the potential to break out of the 2D design space with stacks of 3D devices makes nanomagnetic logic competitive. Keywords: Nanomagnets, Semiconductor, Transistor etc.