W. M. Keck Microfabrication Facility |
CSM MSU PA MSU |
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Research Projects |
Spin-Polarized Transport in Mesoscopic F/N/F Structures
C.E. Moreau, J.A. Caballero, W.P. Pratt, Jr., and Norman O. Birge
Department of Physics and Astronomy and NSF Center for Sensor Materials
Michigan State University
 Figure 1. Photograph with a scanning electron microscope of a sample used to deduce the phase coherence time tf from the low field magnetoresistance. The wire is 270 mm long, 100 nm width and 45 nm thick. The magnetic field is applied perpendicularly to the plane of the wire. |
 Figure 2. Open symbols: measured phase coherence time as a function of temperature in a silver, gold and copper wire. Solid line: fit of the phase coherence time measured on the silver wire using the predicted temperature dependence. Dashed line: theoretical prediction of screened Coulomb interaction for the silver wire. |
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We have measured the magnetoresistance (MR) of hybrid ferromagnetic (F)/ nonmagnetic (N) structures fabricated with a planar geometry, using multi-level electron beam lithography [1]. The samples consist of two single-domain nanofingers crossed by a 200 nm wide Ag wire. The F elements have lengths of 1 µm, widths of 250 and 175 nm respectively, and are placed parallel to each other with a center-to-center spacing of 400 nm. The different widths enable us to change the magnetization direction of the fingers independently. When we apply the current between two F elements via the N wire, the device is somewhat analogous to a traditional F/N/F perpendicular current (CPP) spin valve sandwich. Magneto-transport measurements on our sample show the typical spin valve effect. Though the effect is relatively small for these devices (dR/R = 4x10-4), it is commensurate with theoretical predictions. Also, we gain the advantage of being able to measure several different current-lead configurations in the same sample. These include using multiple F elements to see the dependence of the MR on the distance between the spin injector and detector, as well as an experiment where the current leaves via the normal wire [2].
[1] J.A. Caballero, C.E. Moreau, Norman O. Birge and W.P. Pratt, Jr. (to be published, IEEE Trans. Mag.). | |