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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 Wfi& 8Ptl1f 3.4 STT-DRIVEN MOTION OF MAGNETIC DOMAIN WALLS Yet another manifestation of STT in metallic ferromagnets is a motion of magnetic domain walls traversed by an electrical current. The original prediction of the effect dates back to 1978, when Luc Berger predicted that a spin -polarized current should apply a torque to a magnetic domain wall (Reference 59). In a series of remarkable but only recently appreciated works, Berger set the theoretical (Reference 59-62) and experimental (Reference 63-65) groundwork for current-induced domain wall motion (CIDWM), which is now documented in materials ranging from magnetic semiconductors (Reference 66) to perpendicular-anisotropy superlattices (Reference 67). But the most widely studied materials by far have been metallic ferromag nets (Reference 10, 11, 68 -82), including Py (Ni s1 Fe 19), CoFe, and Co, because of their decades-long ubiquity in magnetic storage technology. The CIDWM effect can be qualitatively understood on the basis of the following arguments. Consider an electrical current flowing between two magnetic domains (A and B) with opposite magnetizations and, thus, traversing a 180-degree magnetic domain wall. The situation is similar to that of a single N/F interface discussed in Section 3.1. While in domain A, sp ins of conduction electrons are preferentially aligned with the magnetic moment of A. Once into domain B, the spins reverse to align with the moment of B. In reversing the electron spins, magnetic moments in the domain wall experience a torque associated with the change in angular momentum that occurs from the rotation of electrons spins. This spin-transfer torque can move the domain wall in the direction of the electron flow . Moving magnetic domain walls with n.rtJ1+ current was proposed as the basis for a A new type of magnetic memory called "racetrack" (Reference 83 ). In contrast to today's hard disk drives (HDD), which rely on spinning motion of a disk to move their magnetic regions where the data is stored past a read head, the racetrack memory exploits the idea of moving magnetically stored data electronically. Figure 11 illustrates the concept of the racetrack. The racetrack is a ferromagnetic nanowire, with data encoded as a pattern of magnetic Raal'track domains along the wire. Current pulses vertJcal race1rack storage array can move the entire pattern along the Figure 11. Racetrack Memory Concept. (Reference 83) wire. The two cartoons of Figure lla show the domain wall patterns in the racetrack befor e and after they have moved past read and write elements. Reading is achieved by measuring the resistance of a tunnel junction element connected to the racetrack (Figure llb); writing (Figure llc), by applying local magnetic fields-for example, the fringing fields of a domain wall moved in another nanowire. If U-shaped nanowires are placed normal to the plane of a chip and arranged into high-density arrays of racetracks (Figure lld), the resulting storage density can be higher than that in solid-state memory devices like flash RAM and B C fa D ]I UNCLASSIFIED/ /FOR OFFl&iilAk Wili 0Plk¥ 12
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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.