Optimizing the giant magnetoresistance of NiFe/Cu/Co pseudo spin-valves prepared by magnetron sputtering

Paul, Amitesh; Damm, Thorsten; Bürgler, Daniel E.; Stein, Simon; Kohlstedt, Hermann; Grünberg, Peter
March 2003
Applied Physics Letters;3/24/2003, Vol. 82 Issue 12, p1905
Academic Journal
We study the dependence of magnetic and magnetotransport properties of NiFe/Cu/Co pseudo spin-valves on the pressure of the Ar sputtering gas during magnetron deposition. The giant magnetoresistance (GMR) ratio as a function of the sputtering pressure behaves nonmonotonically with a maximum of about 4% at an intermediate pressure of 0.87 × 10[sup -2] mbar. Magneto-optic Kerr-effect measurements reveal different coercive fields and independent switching of the Co and NiFe layers. The structural characterization by x-ray scattering shows no significant pressure dependence. However, we observe by atomic force microscopy a variation of the grain structure with increasing sputtering pressure; the grain size first decreases and then the grains start clustering for highest pressures. The reduced coercive field and the lower GMR ratio indicate that the clustered grains have weaker magnetic pinning and increased spin-independent scattering.


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