Characterizations of NiCu/Cu Multilayers: Dependence of Nonmagnetic Layer Thickness
A series of NiCu/Cu multilayers were grown on (110) textured polycrystalline Cu substrates from a single electrolyte under potentiostatic deposition conditions. Microstructure, magnetoresistance and magnetic properties of the multilayers were investigated as a function of the nonmagnetic layer thicknesses. The structural studies by X-ray diffraction revealed that the multilayers have face-centered-cubic structure with preferred (110) crystal orientation as their substrates. The composition of the deposits determined by energy dispersive X-ray spectroscopy showed that the Cu content of the films increased as the Cu layer thickness increased. The scanning electron microscope studies showed that samples have homogeneous and smooth surfaces. Multilayers exhibited either anisotropic magnetoresistance (AMR) or giant magnetoresistance (GMR) depending on the non-magnetic Cu layer thickness. The multilayers with Cu layer thickness thicker than 0.7 nm exhibited GMR, but the AMR effect was observed to be dominant for the Cu layer thickness less than 0.7 nm. The GMR curves are broad in shape and the nonsaturated curves indicated the predominance of a superparamagnetic contribution. The GMR magnitudes of NiCu/Cu multilayers are found to be about 1–1.5 %. The vibrating sample magnetometer measurements revealed that the saturation magnetization decrease with increasing nonmagnetic layer thickness. The changes in the magnetic and magnetotransport properties might arise from the change in the Ni and Cu content of the samples caused by the variation of Cu layer thicknesses.
KeywordsElectrodeposition NiCu/Cu multilayers GMR XRD Magnetic films
This work is supported by Balikesir University, Turkey, under Grant No. BAP 2006/37. The authors would like to thank State Planning Organization, Turkey, under Grant No. 2005K120170 for the VSM system, Scientific and Technical Research Council of Turkey (TUBITAK) under Grant No. TBAG-1771 for the electrodeposition system and Balikesir University, Turkey, under Grant No. BAP 2001/02 for the MR system. Thanks also go to the Material Science and Engineering Department, Anadolu University, Turkey, for the use of XRD and SEM-EDX measurements.
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