The characterizations of structural and magnetoresistance properties of CuCo and Cu-Co-Ni alloys obtained by electrochemical deposition

ABSTRACT Ph.D. Thesis THE CHARACTERIZATIONS OF STRUCTURAL AND MAGNETORESİSTANCE PROPERTIES OF CuCo and CuCoNi ALLOYS OBTAINED BY ELECTROCHEMICAL DEPOSITION Ismail Hakkı KARAHAN Atatürk University Graduate School of Natural and Applied Sciences Department of Physical Education Supervisor : Prof. Dr. Ömer Faruk BAKKALO?LU Nowadays Giant magnetoresistive materials are used in sensor and magnetic read heads. The giant magnetoresistance (GMR) effect is usually observed in systems composed of insoluble elements especially at room tempereture. Co in Cu is an example of such a system, which tend not to make solid solution with each other at equilibrim conditions. The CuCo and CuCoNi alloy films were prepared by electrochemical deposition technique. The variations of Co and Cu contents in film were investigated as a functions of bath pH and Ni content in bath. The composition of the alloy films were determined by an atomic absorbtion spectrophotometer and energy dispersive spectrometer. The crystal structures of the alloy films were analysed by a Cu(Ko)-X-Ray difroctometer. The structural properties were investigated by scanning electron microscopies (SEM). Using the electrical measurements, the longitudunal mr coefficients and electrical resistivity were calculated and investigated. The diffraction lines observed were only those of copper component in alloy films. All films shoved negative magnetoresistance effect while a giant magnetoresistance effect was observed to be %1,9 at value of pH=5,5 CoCu, %1,48 at value of pH=6 CoCu, %2,08 at value of pH=5,25 CoCu and %3,03 at value of pH=6,25 CoCu, %1,25 at (20g/l Ni) NiCoCu, %1,29 in (5 g/1 Ni) CuCoNi, %1,7 in (1 g/1 Ni) CuCoNi alloy films at 20K. It vas also dedected that the magnetoresistance effect initialy increased and then decreased with increasing Co percentage in CuCo alloys and decreased with increasing Ni percentage in CuCoNi alloy films. 2002, 124 pages Keywords : Magnetoresistance, Giant Magnetoresistance (GMR), CuCo alloys, Electrochemical deposition, CuCoNi alloys. ii