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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//fOlt Offl@IAL ~91! OHL¥ currents larger than the critical current, STT exceeds the damping torque and causes__. to spiral away from B eff, with a steadily increasing precession angle. The ultimate... __. result can be either stable steady-state precession of S around B eff (black trajectory in ... -Figure 6) or magnetic reversal of S into a state anti parallel to B eff, depending on the angular dependence of STT and damping torques. Almost all experimental observations of STT rely on the GMR phenomenon to detect the current-induced reorientation of magnetic moments in nanodevices. Typical measurements include (1) measuring static device resistance R= V/I as a function of__. __. applied de bias current I in an applied magnetic field B and (2) measuring R versus B at a constant I. Figure 3 shows how the differential resistance dV/dl of a Cu point contact to Co/Cu magnetic multilayer varies with the bias voltage V (equivalent to I) applied across the contact. Here the multilayer magnetic moments are saturated out of the plane of the layers by a sufficiently large externa l magnetic field (B ;:: 2T). The onset of STT-driven magnetic precession is revealed by a peak in differential resistance of the contact. The peak in dV/dl indicates the transition into precession is a reversible process, and in a small range of currents, one can continuously increase or decrease the angle of precession. However, other scenarios are also possible- for example, fast transitions between static and steady-state precession states with current-dependent dwell time. If the applied magnetic field is small, the magnetic system can have more than one •low -energy state. In the simple case of a 6 a.2 magnetic element with uniaxial anisotropy, STT can trigger a transition -=a 8.1between two static states that are energetically favorable. An example of > .such behavior is shown in Figure 7. Here u 8.0 • - the current is driven across a trilayer Py20nm/Cu12nm/Py4.Snm spin- valve -0.4 -0.2 0.0 0.2 0.4 structure patterned by electron beam I (mA.)lithography into a nanopillar with a 40 x Figure 7. Spin-torque-driven magnetic switching 120 nm 2 cross-sectional area (Reference for a Py20nm/Cu12nm/Py4.5nm spin valve with a 40x120-nm 2 cross-sectional area, as the48). The differential resistance of the magnetization of the thin (free) magnetic layer is nanopillar exhibits a hysteresis as a aligned parallel and antiparallel to the thicker function of an applied bias current as the magnetic layer by an applied current. (Reference magnetization of the thin (free) permalloy 48) (Py) layer is aligned para llel and antiparallel to the thick (hard) Py layer by the current. The two examples presented above (Figures 3 and 7) demonstrate how simple de resistance measurements can be used for STT observation. Here the measured resistance of a device provides indirect information about the relative orientation of magnetic elements in the device . However, measured critical currents highlighted by sharp variations in the resistance remain the only experimental information t hat can be used to quantitatively compare theory and experiment. Moreover, the de measurements in Figure 3 provide no information about fast evolution of magnetization in the device 8 UNCLASSIFIED/ /FOR OFFICIO 1 1!SF Al:!! X
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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.