All Spin Logic device with inbuilt Non-Reciprocity

The need for low power alternatives to digital electronic circuits has led to increasing interest in logic devices where information is stored in nanomagnets. This includes both nanomagnetic logic (NML) where information is communicated through magnetic fields of nanomagnets and all-spin logic (ASL) where information is communicated through spin currents. A key feature needed for logic implementation is non-reciprocity, whereby the output is switched according to the input but not the other way around, thus providing directed information transfer. The objective of this paper is to draw attention to possible ASL-based schemes that utilize the physics of spin-torque to build in non-reciprocity similar to transistors that could allow logic implementation without the need for special clocking schemes. We use an experimentally benchmarked coupled spin-transport/ magnetization-dynamics model to show that a suitably engineered single ASL unit indeed switches in a non-reciprocal manner. We then present heuristic arguments explaining the origin of this directed information transfer. Finally we present simulations showing that individual ASL devices with inbuilt directionality can be cascaded to construct circuits.Comment: 7 pages, 8 figures, To appear in IEEE Trans. Mag

Novel all-spin devices and architectures for low power computing

Power dissipation in switching devices is believed to be the single most important roadblock to the continued downscaling of charge based electronic circuits. At this time there is a lot of interest in analyzing alternative technologies which could enable further downscaling of electronic circuits. It has also been suggested that magnets as collective entities could require significantly low switching energies. In this thesis we analyze the intrinsic switching energy that is dissipated in the switching process of single-domain magnets. One central result is that the intrinsic switching energy of a magnet (which could be composed of millions of spins) is on the order of its energy barrier height Eb. This is different from conventional transistors in that the switching energy is on the order of NE b, N being the number of electronic charges participating in a switching process (usually on the order of thousands). Furthermore a spintronic device is proposed that uses spin at every stage of its operation: information manipulation, transport, storage, input and output are all accomplished with magnets and spin-coherent channels. Contrary to the typical spin/magnet based logic schemes, the all-spin scheme neither relies on ordinary magnetic fields (generated by current carrying wires) nor does it rely on electrical read-out of magnetic states. Binary data are represented by the bi-stable states of nanomagnets (i.e. magnetic polarization) which can be non-volatile. Application of a voltage signal to a magnetic contact (input data bit) creates a spin-current in a channel which can be conveniently guided and routed to another magnetic contact (output data bit) where it determines its final state based on spin-torque phenomenon. The all-spin device could potentially find use for low-power digital logic since it should satisfy the five essential characteristics for logic applications namely nonlinearity, gain, concatenability, feedback prevention and a complete set of Boolean operations. Moreover it could provide a basis for unconventional approaches. For example the spin accumulation in a channel underneath a magnetic contact could provide a weighted average of different inputs that makes it switch (\u27fire\u27) when it exceeds a threshold like neural networks. Alternatively the magnetic contacts on top of the channel could possibly serve as input-output interface for spin-based quantum computing

A design methodology and device/circuit/architecture compatible simulation framework for low-power magnetic quantum cellular automata systems

CMOS device scaling is facing a daunting challenge with increased parameter variations and exponentially higher leakage current every new technology generation. Thus, researchers have started looking at alternative technologies. Magnetic Quantum Cellular Automata (MQCA) is such an alternative with switching energy close to thermal limits and scalability down to 5nm. In this paper, we present a circuit/architecture design methodology using MQCA. Novel clocking techniques and strategies are developed to improve computation robustness of MQCA systems. We also developed an integrated device/circuit/system compatible simulation framework to evaluate the functionality and the architecture of an MQCA based system and conducted a feasibility/comparison study to determine the effectiveness of MQCAs in digital electronics. Simulation results of an 8-bit MQCA-based Discrete Cosine Transform (DCT) with novel clocking and architecture show up to 290X and 46X improvement (at iso-delay and optimistic assumption) over 45nm CMOS in energy consumption and area, respectively