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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/ /P'Olt orr1e1At tt!I!! er~LY associated with high-frequency precession of magnetic moments. High-frequency techniques must be employed to provide such capabilities, as discussed next. The first experiment providing unequivocal evidence that a de electrical current can result in high-frequency (tens of GHz) precession of magnetic moments was reported by Tsoi et al. in (Reference 9). Here an STT device- point contact-was placed in a microwave cavity of a high-frequency, high-field electron spin resonance (ESR) spectrometer. This arrangement allowed performing de transport experiments, such as those described above, while the contact was irradiated with high-frequency microwaves. When the frequency of external microwaves matched the precession frequency excited by the de current, an additional (rectified) voltage was detected across the contact. By detecting this voltage while varying the external frequency, field, and applied current, Tsoi et al. (Reference 9) were able to map the frequency excited by de current as a function of applied field and current. In a more recent experiment, Rippard et al. (Reference 49) fed microwaves to a point contact via electrical leads and reported observation of a similar de response. . .Finally, the high-frequency dynamics of the free-layer magnetization can be 100 .C . measured directly by detecting high frequency oscillations in voltage across a spin valve under de current. Here the hard magnetic layer is fixed, while the >free layer exhibits a high-frequency aprecession relative to the hard layer. Cl) 0. I• GMR results in a high -freq uency mmodulation of the spin-va lve resistance, which in turn leads to a high-frequency -0 component of the voltage across the > spin valve traversed by a de current. This voltage can be directly probed with · 100 •a high-frequency spectrum analyzer, as . .was recently done by Kiselev et al. (Reference SO) and by Rippard et al. 0 5 10 (Reference 41). Moreover the voltage oscillations owing to spin-torque-driven Ti (ns) magnetic precession can be directly Figure 8. Oscillatory Voltage Generated by measured in time domain using a Precessional Motion of the Free Magnet in IrMn8nm/NiFe4nm/Cu8nm/NiFe4nm Nanopillar, insampling oscilloscope (Reference 51), Response to a 335-mV de Voltage Step Applied to as illustrated in Figure 8. the Device at B = 630 Oersteds (Reference 51) The above examples illustrate how broadband instrumentation for measuring voltage in GMR devices may provide important and often unique information about high-frequency magnetic dynamics driven by spin-transfer torques. However, the detailed understanding of STT is still the subject of debate and requires new experimental techniques capable of probing magnetization dynamics on nanometer length scales and sub-nanosecond time scales. In principle, this can be accomplished by the use of synchrotron x-rays that were recently shown (Reference 52) to probe interfacial phenomena and directly image the time-resolved response of magnetic nanostructures to sub-nanosecond magnetic field pulses (Oersted switching) and spin-polarized current 9 UNCLASSIFIED/ /FOA 8FFIGIAb W&E 8,.b\S
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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.