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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 OFFIElIAk WSE OPtkY The original observation of the effect was reported by Wei et al. (Reference 91), who measured magnetoresistance of a po int contact to EBSV film at room temperature ( ~ 295K) with negative current flowing from the contact t ip into the film. The sample geometry is shown in Figure 12a. A point contact is used to inject a de current into a sputtered N/Fl/N/F2/AFM/N = Cu(50 or 100nm)/CoFe(3 or 10nm)/Cu(10nm)/CoFe(3 or l0nm)/FeMn (3 or 8nm)/Au(5nm) multilayer (or inv,erted versions thereof-that is, Cu/FeMn/CoFe/Cu/CoFe/Au). The sample is heated to ~ 450K (above the blocking temperature of FeMn) and then cooled in a magnetic field of 180 Oersteds to exchange bias the "pinned" layer F2 to a higher magnetic field than needed to reverse the "free" layer F2. The top layer is covered by a 5-nm-thick layer of Au to protect it from atmospheric contamination. The magnetic field H is applied in the plane of the layers and along the direction of exchange bias . Magnetic coupling between the two F layers should be negligible, because the N layer is thick enough (10 nm) to el iminate exchange coupling, and the two Flayers are wide enough ( ~ mm) to minimize dipolar coupling. The bottom N layer is Cu, made thick enough (50 or 100 nm) to approximate an equipotential, thereby generating an approximately CPP current flow through the Fl/N/F2/AFM EBSV. J F1 - N F2 - AFM - ----N "° 20 e , ,,,,, ·60 I I 0 ·20 0 30 0 .30 10 l0 -10 - 20 0 ·20 B (mTJ B (mT) Figure 12. (a) Schematic of point contact to sample geometry. Omitted is a 5-nm-thick protective Au capping layer between the point contact and the multilayer. The bottom N layer is also much thicker than shown to help produce a nearly CPP current. (b) R (vertical scale) versus applied magnetic field B for a series of currents I. The solid black curves are hysteresis curves starting from large positive Band finishing at large negative B. The grey curves start at large negative B and finish at positive B. In the dark curves, the "free" layer, Fl, switches at ,.., -5 mT and the pinned layer, F2, switches at fields ranging from below -40 mT (large positive I) to about - 60 mT (large negative I). (c-e ) Grey-scale plots of R versus B for different values of I. White is maximum R (antiparallel state) and black is minimum R (parallel state). Lines are linear fits to the data at 30 percent (dashed white), SO percent (solid white) and 70 percent (dashed black) of maximum R. Sample (c) is the sample of (b), with the AFM layer on the bottom (furthest from the point contact). Sample (d} Is similar to (c), except inverted, so that the AFM layer is on top (closest to the point contact). Sam ple (e) differs from (b) only in that it has two equally thick (8-nm) F layers. (Reference 91) Figure 12b shows magnetoresistance curves for a series of currents I appl ied to a point contact with resistance R = 0. 92 n. The dark curves show sweeps from positive to negative fie ld, and the lighter curves show sweeps back down from negative to positive field. For this contact, I = 30 mA corresponds to j ~ 2 x 108 A/cm 2. For dark curves, a large positive field + B along the pinning direction causes the moments of both the "free" and "pi nned" F layers to point along +B, produci ng t he minimum resistance RP in this para llel orientation of the two Fs. Reducing the magnitude of B, the "free" F2 layer reverses at a small-magn itude negative B, giving the maximum resistance RAP in antipara ll el configuration. Finally, a larger magnitude negative B breaks the exchange bias pinning of the "pinned" Fl layer, and its moment rotates to along -B, returning the UNCLASSIFIED/ ,' FOA OfifilCI0Lt !P&i Alf! Y 15
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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.