CoFeNi/Cu süperörgülerin özelliklerinin Ni içeriğine bağlı olarak incelenmesi



















































































ii
ABSTRACT
In this study, CoFeNi/Cu superlattices were grown on Ti (hexagonal closed packet-hcp) substrates from electrolytes containing their own ions by the electrochemical deposition technique. The properties of the superlattices were investigated as a function of the Ni ion concentrations in the electrolyte, the Cu (nonmagnetic) and CoFeNi (ferromagnetic) layer thicknesses. The deposition potentials of metals vs saturated calomel electrode (SCE) were determined to be -1.5 V for the ferromagnetic layers and -0.3 V for non-magnetic layers, using the cyclic voltammetry method (CV).
The structural characterizations of samples were studied using X-ray Diffraction (XRD). The (111), (200), (220) and (311) peaks of face centred cubic (fcc) crystal structure were clearly observed in XRD patterns of films and therefore all films have only fcc phase. The crystal orientations of CoFeNi/Cu superlattices grown from the electrolytes containing different Ni ions were calculated and seen to have the (111) orientation as in bulk Co and Ni. Since the Ni content of the film increase, as the Ni concentration in the electrolyte is increased, the lattice constant of the film approached to that of the bulk Ni (0.3524 nm).
The magnetic characterizations of samples were measured by the vibration sample magnetometer (VSM) technique. When the Ni concentration is increased from 0 M to 0.1 M, the coercivity values approach to the soft ferromagnetic limit (12.5 Oe), due to the soft ferromagnetic Co (20 Oe).
The magnetoresistance (MR) characterizations of the samples were studied by the van der Pauw technique. All superlattices exhibited giant magnetoresistance (GMR), which arises from their periodic structure. The GMR magnitude for a superlattice with 375[CoFe(4 nm)/Cu(4 nm)] grown from a non-Ni electrolyte is 16 %, but this value rises up to 22% for a superlattice with 375[CoFeNi(4 nm)/Cu(4 nm)] grown from the electrolyte containing 0.5 M Ni. When the Ni concentration in the electrolyte is increased from 0.5 M to 1.0 M, the GMR value decreases down to 9%. In addition, the magnetoresistance measurements of the samples were performed as a function, both Cu and CoFeNi layer thickness. The CoFeNi layer thickness was held constant at 4 nm, while the thickness of the Cu layer was changed from 0.5 to 4 nm. For this series, the largest GMR value was obtained when Cu layer thickness was 4 nm. On the other hand using the same solution, when the Cu layer thickness was fixed at 4 nm and the CoFeNi layer thickness was changed from 2 nm to 15 nm, the maximum GMR value was found for the CoFeNi layer thickness of 4 nm.
Key Words: Electrodeposition, GMR, CoFeNi/Cu superlattices, the effect of Ni content
in CoFe/Cu systems.



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Co/Cu çok katmanlı nanoyapılar üzerine Fe içeriğinin etkisi - Sayfa 5
ii ABSTRACT In this study, CoFe/Cu ferromagnetic multilayered structures were grown on polycrystalline Ti (hcp) substrates from electrolytes containing their ions by the electrochemical synthesis technique. The properties of the films were investigated as a function of the concentrations of Fe, magnetic and non-magnetic layers thickness. The deposition potentials of metals vs saturated calomel e...
CoNi/Cu süperörgülerinin elektrodepozisyonu ve magnetorezistans özellikleri - Sayfa 6
ABSTRACT MSc Thesis ELECTRODEPOSITION and MAGNETORESISTANCE PROPERTIES OF CoNi/Cu SUPERLATTICES Elif ŞENTÜRK Uludağ University Graduate School of Natural and Applied Sciences Departmant of Solid State Physics Supervisor: Prof. Dr. Mürsel ALPER CoNi/Cu superlattices were grown on Ti (hcp) substrates from electrolytes containing their own ions by the electrodeposition technique. The propertie...
Elektrodepozisyonla sentezlenen NiFe alaşım ve NiFeCu/Cu süperörgülerin yapısal, manyetik - Sayfa 5
ABSTRACT STRUCTURAL, MAGNETIC AND MAGNETOTRANSPORT CHARACTERIZATION OF THE NiFe ALLOYS AND NiFeCu/Cu SUPERLATTICES SYNTHESISED BY ELECTRODEPOSITION Hilal KURU Balıkesir University,Institute of Science, Department of Physics (Phd. Thesis/Supervisor: Assoc. Prof. Dr. Hakan KÖÇKAR) (Second Supervisor:Prof. Dr. Mürsel ALPER) Balıkesir, 2009 In this study, the electrodeposition and structural, mag...

5. SAYFADAKI ANAHTAR KELIMELER

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5. SAYFA ICERIGI

ii
ABSTRACT
In this study, CoFeNi/Cu superlattices were grown on Ti (hexagonal closed packet-hcp) substrates from electrolytes containing their own ions by the electrochemical deposition technique. The properties of the superlattices were investigated as a function of the Ni ion concentrations in the electrolyte, the Cu (nonmagnetic) and CoFeNi (ferromagnetic) layer thicknesses. The deposition potentials of metals vs saturated calomel electrode (SCE) were determined to be -1.5 V for the ferromagnetic layers and -0.3 V for non-magnetic layers, using the cyclic voltammetry method (CV).
The structural characterizations of samples were studied using X-ray Diffraction (XRD). The (111), (200), (220) and (311) peaks of face centred cubic (fcc) crystal structure were clearly observed in XRD patterns of films and therefore all films have only fcc phase. The crystal orientations of CoFeNi/Cu superlattices grown from the electrolytes containing different Ni ions were calculated and seen to have the (111) orientation as in bulk Co and Ni. Since the Ni content of the film increase, as the Ni concentration in the electrolyte is increased, the lattice constant of the film approached to that of the bulk Ni (0.3524 nm).
The magnetic characterizations of samples were measured by the vibration sample magnetometer (VSM) technique. When the Ni concentration is increased from 0 M to 0.1 M, the coercivity values approach to the soft ferromagnetic limit (12.5 Oe), due to the soft ferromagnetic Co (20 Oe).
The magnetoresistance (MR) characterizations of the samples were studied by the van der Pauw technique. All superlattices exhibited giant magnetoresistance (GMR), which arises from their periodic structure. The GMR magnitude for a superlattice with 375[CoFe(4 nm)/Cu(4 nm)] grown from a non-Ni electrolyte is 16 %, but this value rises up to 22% for a superlattice with 375[CoFeNi(4 nm)/Cu(4 nm)] grown from the electrolyte containing 0.5 M Ni. When the Ni concentration in the electrolyte is increased from 0.5 M to 1.0 M, the GMR value decreases down to 9%. In addition, the magnetoresistance measurements of the samples were performed as a function, both Cu and CoFeNi layer thickness. The CoFeNi layer thickness was held constant at 4 nm, while the thickness of the Cu layer was changed from 0.5 to 4 nm. For this series, the largest GMR value was obtained when Cu layer thickness was 4 nm. On the other hand using the same solution, when the Cu layer thickness was fixed at 4 nm and the CoFeNi layer thickness was changed from 2 nm to 15 nm, the maximum GMR value was found for the CoFeNi layer thickness of 4 nm.
Key Words: Electrodeposition, GMR, CoFeNi/Cu superlattices, the effect of Ni content
in CoFe/Cu systems.

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