The role of nucleation in the evolution of giant magnetoresistance with layer thicknesses in electrodeposited Co-Cu/Cu multilayers

Q. X. Liu, L. Péter, J. Tóth, L. F. Kiss, Á Cziráki, I. Bakonyi

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

Electrodeposited Co-Cu/Cu multilayers were prepared by a galvanostatic/potentiostatic (G/P) pulse sequence in which the Co-rich magnetic Co-Cu layer was deposited by current control and the non-magnetic Cu layer by potential control. The Cu deposition potential has been chosen so as to exclude the occurrence of a Co dissolution during the Cu deposition cycle. This ensured that the actual amounts of metals deposited were equal to the nominal ones. The multilayers with a total thickness of about 1.7μm were mechanically peeled off from their Ti substrate. Detailed room-temperature studies of the dependence of the magnetoresistance (MR) and the magnetic properties on Co and Cu layer thicknesses were performed with particular attention to analysing the field evolution of the MR. A giant magnetoresistance (GMR) effect was observed in most samples and a maximum GMR of 10% measured at 1kOe could be achieved. No oscillatory GMR behaviour with increasing Cu layer thickness could be observed but rather a continuous evolution of the MR characteristics from anisotropic magnetoresistance (AMR) to GMR. This could be explained by the gradual increase of the Cu coverage on the Co-rich magnetic layer during each Cu pulse with increasing average Cu layer thickness. It was concluded that the Cu layer becomes continuous above about 2nm thickness only. For 2.5nm Cu layer thickness, the Co layer remained continuous down to 1.1nm thickness. However, for 1.1nm Cu layer thickness, the 1.1nm thick Co layer was broken up into superparamagnetic islands. The evolution of the coercive force with layer thicknesses well corroborated the above picture. From these results, an asymmetry in the nucleation of Cu on Co and Co on Cu could be deduced in agreement with some previous reports on evaporated multilayers.

Original languageEnglish
Pages (from-to)60-74
Number of pages15
JournalJournal of Magnetism and Magnetic Materials
Volume280
Issue number1
DOIs
Publication statusPublished - Sep 1 2004

Keywords

  • Co-Cu/Cu multilayers
  • Electrodeposition
  • GMR
  • Magnetic hysteresis
  • Nucleation and growth

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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