We describe the operation of, and demonstrate logic functionality in, networks of physically coupled, nanometer-scale magnets designed for digital computation in magnetic quantum-dot cellular automata (MQCA) systems. MQCA offer low power dissipation and high integration density of functional elements and operate at room temperature. The basic MQCA logic gate, that is, the three-input majority logic gate, is demonstrated.

Histidine decarboxylase (HDC) synthesizes histamine from histidine in mammals. To evaluate the role of histamine, we generated HDC-deficient mice using a gene targeting method. The mice showed a histamine deficiency and lacked histaminesynthesizing activity from histidine. These HDC-deficient mice are viable and fertile but exhibit a decrease in the numbers of mast cells while the remaining mast cells show an altered morphology and reduced granular content. The amounts of mast cell granular proteases were tremendously reduced. The HDCdeficient mice provide a unique and promising model for studying the role of histamine in a broad range of normal and disease processes. ß

Quoting the International Technology Roadmap for Semiconductors (ITRS) 2009 Emerging Research Devices section, 'Nanomagnetic logic (NML) has potential advantages relative to CMOS of being non-volatile, dense, low-power, and radiation-hard. Such magnetic elements are compatible with MRAM technology, which can provide input–output interfaces. Compatibility with MRAM also promises a natural integration of memory and logic. Nanomagnetic logic also appears to be scalable to the ultimate limit of using individual atomic spins.' This article reviews progress toward complete and reliable NML systems. More specifically, we (i) review experimental progress toward fundamental characteristics a device must possess if it is to be used in a digital system, (ii) consider how the NML design space may impact the system-level energy (especially when considering the clock needed to drive a computation), (iii) explain--using both the NML design space and a discussion of clocking as context—how reliable circuit operation may be achieved, (iv) highlight experimental efforts regarding CMOS friendly clock structures for NML systems, (v) explain how electrical I/O could be achieved, and (vi) conclude with a brief discussion of suitable architectures for this technology. Throughout the article, we attempt to identify important areas for future work.

We demonstrate through simulations the feasibility of using magnetically coupled nanometer-scale ferromagnetic dots for digital information processing. Microelectronic circuits provide the input and output of the magnetic nanostructure, but the signal is processed via magnetic dot-dot interactions. Logic functions can be defined by the proper placements of dots. We introduce a SPICE macromodel of interacting nanomagnets and use this tool to design and simulate the proposed nanomagnet logic units. This SPICE model allows us to simulate such magnetic information processing devices within the same framework as conventional electronic circuits.Index Terms-Magnetic memories, micromagnetic design, patterned magnetic media, quantum-dot cellular automata, single-domain approximation, SPICE macromodel.

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The search for novel tools to control magnetism at the nanoscale is crucial for the development of new paradigms in optics, electronics and spintronics. So far, the fabrication of magnetic nanostructures has been achieved mainly through irreversible structural or chemical modifications. Here, we propose a new concept for creating reconfigurable magnetic nanopatterns by crafting, at the nanoscale, the magnetic anisotropy landscape of a ferromagnetic layer exchange-coupled to an antiferromagnetic layer. By performing localized field cooling with the hot tip of a scanning probe microscope, magnetic structures, with arbitrarily oriented magnetization and tunable unidirectional anisotropy, are reversibly patterned without modifying the film chemistry and topography. This opens unforeseen possibilities for the development of novel metamaterials with finely tuned magnetic properties, such as reconfigurable magneto-plasmonic and magnonic crystals. In this context, we experimentally demonstrate spatially controlled spin wave excitation and propagation in magnetic structures patterned with the proposed method.

Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first Roadmap on Magnonics. This a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This Roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.