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The Defense Intelligence Agency's Defense Warning Office issued this Defense Intelligence Reference Document, dated 23 March 2010, as one of a series of advanced technology reports produced in FY 2009 under its Advanced Aerospace Weapon System Applications Program. The report reviews metallic spintronics, including giant magnetoresistance, spin-transfer-torque and antiferromagnetic spintronics, along with their applications. It concludes that spintronic devices could offer radiation-resistant, low-power electronics suited to aerospace use and long space trips.
From the source: Release of 2026-09-18 Incident: 3/23/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys metallic spintronics, a branch of electronics that seeks to use both the electric charge and the magnetic spin of electrons to store, detect, and manipulate information, and argues that the field could lead to faster, lower-power, and more radiation-resistant devices than conventional semiconductor electronics. The report focuses on two main effects: giant magnetoresistance (GMR), which allows magnetic states to be read through changes in electrical resistance, and spin-transfer torque (STT), which allows electrical currents to change those magnetic states. The DIRD reviews their underlying physics, the experimental work then available, and possible applications in memory, sensors, oscillators, and logic devices. The document treats metallic spintronics as a promising field while emphasizing that many of its more advanced proposed applications still require substantial further development.
UNCLASSIFIED//FOA OFFl&ilAk Wlili O,.kY 3 . Spin-Transfer-Torque This section focuses on the spin-transfer-torque (STT) phenomenon, which refers to a novel method to control and manipulate magnetic moments in nanostructures by spin currents-one of the forefront and most exciting areas in magnetism research today. 3.1 STT BASICS The previous section showed that the magnetic state of a ferromagnet can affect its electrical transport properties; for instance, the relative orientation of the magnetic moments in magnetic multilayers underlies the phenomenon of GMR (Reference 1, 2). The inverse effect, in which a large electrical current density can perturb t he magnetic state of a multilayer, has also been predicted (Reference 3, 4). Here the current transfers vector spin between the magnetic layers and induces precession and/or reversal of the layer magnetizations. Altering the magnetic state with spin currents is based on quantum mechanical exchange interaction and represents a novel method of magnetization control on the nanometer length scale and the picosecond time scale. 45 ,---,---,---,---,---,--,,---,--~-,---,---,---,The first observation of such a spin transfer phenomenon in magnetic multilayers was recorded by Tsoi et al. 44 (Reference 5) (see Figure 3). In this experiment, the spin-transfer-induced 43 excitations were produced by injecting a 42high-density electrical currents into a -Co/Cu magnetic multilayer through a ~ mechanical point contact. Point contacts ~ 41 smaller than 10 nanometers (nm) are formed when a sharpened Cu metal 40 wire (tip) is carefully brought into contact with the multilayer. The 39 extremely sma ll cross-sectional area of 38~~~~~-~~~~~~-~ such a contact makes it possible to -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 achieve current densities in excess of 1012 A/m 2. Because of its extremely VM sma ll size ( <10 nm), point contact is a Figure 3. Differential Resistance dV / di of a very efficient probe of electrical Mechanical Point Contact as a Function of Current transport properties in ext remely small for a Series of Magnetic Fields. The peak In dV/dl ind icates the onset of SST excitations. The inset showssample volumes inaccessible with other that t he threshold cu rrent at t he peak In dV/dl Increases techniques (for example, electron linearly with the applied field. (Reference 5) beam -lithography patterning). The latter qualifies point contact as the smallest probe of STT today. The STT phenomenon currently attracts considerable attention because it combines poorly understood fundamental science questions with the promise of applications in a broad range of technologies. In high-speed, high-density magnetic recording technology, for instance, SST could replace the Oersted field currently used for writing magnetic bits in storage media (for example, in magnetic random access memory [MRAM]). This may lead to a sma ller and faster magnetic memory. Another possible application is based on the spin -transfer-induced precession of magnetization, which 4 UNCLASSIFIED/ /P'Olt Offl@IAL ~SE 8PtLY
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 27 pages are in the text index: search them above, or from the library's search.