DIRD_10_Metallic_Spintronics.pdf

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23 March 2010 
ICOD: 1 December 2009 
DIA-08-1003-011 
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Defense 
Intelligence 
Reference 
Document 
Acquisition Threat Support 
Metallic Spintronics 
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UNCLASSIFIED,l/FOR OFFICIO! 1155 At'! Y 
Metallic Spintronics 
Prepared by: 
(b)(3):10 USC 424 
gency 
Author: 
Administrative Note 
COPYRIGHT WARNING: Further dissemlnatlon of the photographs in this publication is not authorized. 
This product is one in a series of advanced technology reports produced in FY 2009 
under the Defense Intelligence Agency, J<b)(3):10 USC 424 
I Advanced Aerospace 
Weapon System Applications (AAWSA)rogram. Comments or questions pertaining to 
this document should be addressed to b 3 :10 USC 424· b 6 
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UNCLASSIFIED /qtin@iteQiieinitoldiield ie hbies Contents 1. Introduction........ eusavesunnesses emennenenae eananenananenans nenanesans va haua sana cacanananenaucnnnasananananenenes iv 2. Giant Mag metoresiStance ......ccvecscsersscsuresuserecersperssevepenusceucerereraresresesusscevanssesesenes 1 2.1 GMR BASICS weccaseunenane eenan SARE RR EE BEE eee SURES Ee Ree @Gansnauara nanena PPE REE TSI TELCE CATE ETERS 1 Z.2 GMR Applications ......cccnccescscscscresuceseseeesscuseensnveccouseveneneresurssenesssuseveranccseuseete 3 3. Spin-Transfer-Torque oi cscccucsscesseceesseenecneanseaeee se eeee…

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Metallic Spintronics 
1. Introduction 
The rapid pace of progress in the computer industry over the past 40 
years has been based on the miniaturization of chips and other 
computer components. Further miniaturization, however, faces 
serious challenges-for example, increasingly high power dlsslpation. 
To continue on pace, the industry must go beyond incremental 
improvements and embrace radically new technologies. A promising 
nanoscale technology known as spintronics (a neologism for "spin-
based electronicsu) has emerged. Spintronics refers to the role…

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Spintronics is a broad research field with ( currently) three major 
subfields: ( 1) materials research that is attempting to create new 
materials that are both magnetic and semiconductors, (2) research 
on novel magnetotransport effects in ferromagnetic metals, and (3) 
research on techniques that can be used to manipulate individual 
electron spins. The first subfield is targeting magnetic 
semiconductors because devices based on such materials would be 
the easiest to integrate with the present semiconductor device 
technology and processing capa…

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2. Giant Magnetoresistance 
2.1 GMR BASICS 
This section discusses the phenomenon of giant magnetoresistance (GMR). Excellent 
reviews of GMR are available elsewhere (Reference 12-22). The focus on physical 
concepts important for the sections to follow are discussed. 
GMR in magnetic multilayers refers to a dramatic reduction in the resistance of the 
multilayers when subjected to an external magnetic field. GMR's size is usually defined 
as the resistance change in magnetic field relative to its peak value. The effect can be 
distinguished from the or…

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studies (Reference 30} on sputtered cobalt-copper (Co/Cu) multilayers revealed 
magnetoresistances at room temperatures 3 to 4 times larger than those for iron-
chromium and 13 times greater than those for the permalloy films that were used as 
magnetoresistive sensors in magnetic reading heads at that time. The much higher 
numbers observed in magnetic multilayers predetermined the fate of GMR in magnetic 
recording technology. 
The current understanding is that GMR 
observed in magnetic multilayers arises 
from the dependence of the resistivity 
on …

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r)2/(R+r)2 5 1. The other definition l!R/R = (RAF-RF)/RF::;; (R-r)2/4Rr (unbounded from 
above) is also in use. Figure 2a shows a magnetoresistance curve typical for magnetic 
multilayers. The resistance is constant at a minimum value RF above a saturation field 
Bs (parallel Fs) and rises to a maximum value RAF as the applied magnetic field B 
approaches zero {antiparallel Fs). 
GMR occurs in two different geometries (see Figure 1): namely when the current flows 
in the plane of the layers, or CIP geometry, or when current flows perpendicular to the 
…