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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//FOR OFFl@IAL ~81: 8HLY 3 .2 STT EXPERIMENTS Section 3.1 introduced the physics of STT in magnetic nanosystems. We have seen that a high-density electrical current can result in torques on magnetic elements of the system . These torques may be used to control and manipulate the system's magnetic state . However, the resulting behavior of the system can differ significantly from case to case, depending on particular conditions of observation. For instance, in modest external magnetic fields, magnetization of a small element can be repeatedly reversed between two stable configurations, while at higher fields, where the reversal is energetically unfavorable, the moment can be set into precession at a very high ... frequency . To understand details of what happens with a magnetic moment S in a particular situation, one can use Newton's Second Law. ... ... For S this would be the Landau-Lifshitz-Gilbert equation, where the rate of change of S ... is set equal to the net torque acting on S : Equation 1: Here the first term on the right is the... torque on a magnetic moment S in an ~ effective magnetic field B eff, (including applied, demagnetizing, anisotropy, and other fields), with y the gyromagnetic STT • • ratio; the second term is a phenomenological damping term introduced by Gilbert, with a. the Gilbert damping parameter; ~e thir~ term is the SST where small s· and * are unit Damping vectors along and the polarizer ' *, I is the current, μs is the Bohr magneton, e is the electron charge, and 11 is the spin -polarization factor. The diagram in Figure 6 shows the directions of the three torques from Equation 1. Note that, depending on the polarity of applied current, the STT Figure 6. liorques on a Magnetic Moment in a torque can be either in the same or Magnetic Field and Subject to an Electrical Current opposite direction as the damping torque . In the former case, STT will effectively result in an increased damp~ng for any magnitude of the applie~ current and suppress any possible excitations of from its equilibrium state along B eff. If, however, the STT torque is opposite to the damping, we can distinguish two situations. For currents below a critical current, where STT is... ~ sma ll compared with damping, S spirals toward B eff (red traj ectory in Figure 6). For UNCLASSIFIED/ /&Olil OfifilCI\L: Wii OPIL:¥ 7
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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.