PERPENDICULAR GIANT MAGNETORESISTANCE OF MICROSTRUCTURED PILLARS IN FE-CR AND CO-CU MAGNETIC MULTILAYERS

We have fabricated pillar-like microstructures of Fe-Cr and Co-Cu magn etic multilayers and measured the giant magnetoresistance effect with the current perpendicular to the multilayer plane. Lithographic and re active ion etching techniques were used to define ''pillars'' with a h eight of typically 0.5 mu m and a width ranging between 3 and 10 mu m. The perpendicular current density pattern in these structures was mod elled analytically, providing an accurate description of the scaling o f the experimental resistance with pillar size. The perpendicular gian t magnetoresistance effect was determined as a function of temperature from 4 to 300 K. For both Fe-Cr and Co-Cu multilayers, we found, at l ow temperature, magnetoresistance effects of the order of 100%. The Fe -Cr pillars showed a pronounced decrease in magnetoresistance with tem perature, whereas for Co-Cu the temperature dependence was much weaker ; this is due to the fact that, for our Co-Cu multilayers, the thermal ly induced scattering is more spin dependent than for Fe-Cr. Finally, we compared our microfabrication approach of the perpendicular magneto resistance experiment with the superconducting contacting technique de veloped at Michigan State University.