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Magnetoresistance and structural study of electrodeposited Ni-Cu/Cu multilayers

Jafari Fesharaki, Marjaneh and Péter, László and Schucknecht, Torsten and Rafaja, David and Dégi, Júlia and Pogány, Lajos and Neuróhr, Katalin and Széles, Éva and Nabiyouni, Gholam Reza and Bakonyi, Imre (2012) Magnetoresistance and structural study of electrodeposited Ni-Cu/Cu multilayers. Journal of The Electrochemical Society, 159 (3). D162-D171. ISSN 1945-7111 (online), 0013-4651 (nyomtatott)

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Abstract

Electrodeposition was used to produce Ni Cu/Cu multilayers by two-pulse plating (galvanostatic/potentiostatic control) from a single sulfate/sulfamate electrolyte at an optimized Cu deposition potential for the first time. Magnetoresistance measurements were carried out at room temperature for the Ni Cu/Cu multilayers as a function of the Ni Cu and Cu layer thicknesses and the electrolyte Cu2+ ion concentration. Multilayers with Cu layer thicknesses above 2 nm exhibited a giant magnetoresistance (GMR) effect with a dominating ferromagnetic contribution and with low saturation fields (below 1 kOe). A significant contribution from superparamagnetic (SPM) regions with high saturation fields occurred only for very small nominal magnetic layer thicknesses (around 1 nm). The presence of SPM regions was concluded from the GMR data also for thick magnetic layers with high Cu contents. This hints at a significant phase-separation in Ni-Cu alloys at low-temperature processing, in agreement with previous theoretical modeling and experiments. Low-temperature measurements performed on a selected multilayer down to 18 K indicated a strong increase of the GMR as compared to the room-temperature GMR. Structural studies of some multilayer deposits exhibiting GMR were performed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns of Ni Cu/Cu multilayers exhibited in most cases clear satellite peaks, indicating a superlattice structure which was confirmed also by cross-sectional TEM. The deterioration of the multilayer structure revealed by XRD for high Cu-contents in the magnetic layer confirmed the phase-separation concluded from the GMR data.

Item Type: Article
Subjects: Q Science / természettudomány > QC Physics / fizika > QC04 Electricity. Magnetism. Electromagnetism / villamosság, mágnesesség, elektromágnessesség
Q Science / természettudomány > QC Physics / fizika > QC06 Physics of condensed matter / szilárdtestfizika
Q Science / természettudomány > QD Chemistry / kémia > QD02 Physical chemistry / fizikai kémia
Depositing User: Péter László
Date Deposited: 27 Jan 2012 08:01
Last Modified: 26 Sep 2012 09:59
URI: http://real.mtak.hu/id/eprint/2757

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