Magnetoresistance multilayers

Metallic multilayers. In Section 7.4, we have met the recent discovery of multilayers of two kinds of metal, or of a metal and a non-metal, that exhibit the phenomenon of giant magnetoresistance. This discovery is one reason why the preparation and exploitation of such multilayers have recently grown into a major research field. 

ELECTRICAL CONDUCTIVITY OF INHOMOGENEOUS SYSTEMS APPLICATION TO MAGNETIC MULTILAYERS AND GIANT MAGNETORESISTANCE... 

W. H. Butler, X.-G. Zhang, D. M. C. Nicholson, T. C. Schulthess, and J. M. MacLaren, Giant Magnetoresistance from an Elecuon Waveguide Effect in Cobalt-Copper Multilayers , Physical Review Letters 76, pp.3216-3219, (1996). 

The third example of new technology with increasing interest is electrodeposition of multilayers. For example, Schlesinger et al. (29) have shown that this technology can be applied to produce systems with nanometer-scale structural and compositional variations. Giant magnetoresistance (GMR) in electrodeposited Ni/Cu and Co/Cu multilayers was reported by Schlesinger et al. (28). Those constructs have a number of immediate applications in the areas of sensors as well as nanometer-scale electronic circuitry. For a more complete reference fist as well as apphcations to date, see the review article by Schwartzacher and Lashmore (30). 

Figure 17.6. Oversimplified model of the magnetoresistance in superlattice multilayers. (From M. Schlesinger, Chapter 14 in Electrochemical Technology, T. Osaka, ed., with permission from Kodansha Ltd.)...

Figure 17.9. Maximum (saturation) value of the giant longitudinal magnetoresistance (GMR) in electrochemically grown Co/Cu multilayers as a function of Cu layer thickness. Cobalt layer thickness is held constant at 20 A per layer. The continuous curve is the corresponding RKKY function. (From Ref. 6b, with permission from the Electrochemical Society.)...

Fig. 51. Comparison between the normalised magnetostriction and the normalised magnetoresistance of a Tbo.4Feo.6(8 nm)/Feo 5CoQ 5(9 nm) multilayer annealed at 250°C. After Ludwig and Quandt (2000).

It is also possible to electrodeposit multilayers in cylindrical pores of a suitable etched polymer membrane. Typically, wires with diameters of about 100 nm and length of 5-10 fim can be obtained. The deposition cycles are similar to the ones described above. Magnetoresistance [this is a term describing the relative decrease (increase) in electrical resistance of a material when subjected to a magnetic field longitudinally (transversely) to the current flow] measurements with the current perpendicular to the planes are possible. In addition, giant magnetoresistance (GMR defined below) effects may be observed as well. 

Materials with colossal magnetoresistance for application in different types of sensors in manganites in particular were addressed in talks by I. Troyanchuk and V. Shah (Magnetism of multilayered magnetic films). 

Blondel, A., Meier, J. P., Doudin, B., and Ansermet, J.-Ph., Giant magnetoresistance of nanowires of multilayers. Appl. Phys Lett. 65,3019 (1994). 

Piraux, L., George, I. M., Despres, X F., Leroy, C., Ferain, E., Legras, R., Ounadjela, K., and Fert, A., Giant magnetoresistance in magnetic multilayered nanowires. Appl. Phys. Lett. 65,2484 (1994). 

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