Magnetoresistance effect CuAgCo allo films

The electrodeposition technique was employed to grow magnetic CuAgCosystems. The deposition was performed on Al substrate using a computer controlledpotensiostat/galvanostat. Three types of CuAgCo films were grown by varying i) Cocontent in bath, ii) the bath pH and iii) the deposition current density. Compositionalanalyses indicate that all our films are mainly composed of Cu and Co elements. Theamount of silver component in each system was at most 1%. The amount of Agcomponent in any film did not increase even when Co and Cu contents in bath werevaried, and the magnitude of Ag component persisted around 1% in all the filmsgrown in this study. SEM studies show that the CuAgCo films have granular nature.The magnitude of the MR value in our films varied between 0.3% and 1% forthe films of the Co variation from 25g/l to 50g/l, between 0.5% and 0.9% for thefilms of the pH variation of 5.2 to 6 and between 0.3% and 0.8% for the films of thecurrent variation between 2.5 and 4.5 mA/cm2. In the longitudinal and transverse MRmeasurements generally an isotropic behavior was detected. Although the isotropicbehavior mainly indicates the GMR presence, a small anisotropic magnetoresistance(AMR) component was also detected in some of the films. The presence of AMRmay be attributed to the coalescence of Co grains under the certain preparationconditions: Above certain threshold limits of the amount of Co component in bath,the pH value and the deposition current density, the connection of the magneticgrains may be formed. Above the 32% Co content in the film and above the bath pHvalue of 5.6, a decrease in MR effect and the presence of anisotropic MR effect werevidetected while below these values of the Co content and pH, the CuAgCo films showisotropic and increasing MR effect with increasing Co content and pH. An irregularvariation of the MR effect was seen in the current variation films. From the MRcurves it may therefore be deduced that below the 32% Co content and below the pHvalue of 5.6, the magnetic Co entities in our films form superparamagnetic grainswhereas the Co grains may be connected to each other to form ferromagneticallycoupled grains in these films with the Co content higher than 32% and in the filmswith the pH value higher than 5.6 which results in the creation of AMR.In the analysis of our superparamagnetic CuAgCo films which have Co contentless than 32% or were prepared with a pH value less than 5.6, the assumption of thesuperparamagnetic behavior of small magnetic Co grains was employed. From thisanalysis, the average magnitude of Co grain was obtained to be between 9 Å and10Å. Any correlation between the surface to volume ratio of Co grains and thehighest MR at 10kOe was not detected but a linear increase in the MR value at10kOe with the increasing Co grain concentration was found in the CuAgCo films ofCo and pH variations.Keywords: Giant magnetoresistance, Electrodeposition, CuAgCo Thin Filmsvii