Relevant GMR in As-Deposited Co−Ag Electrodeposits: Chronoamperometric Preparation

Abstract

Electrodeposited Co-Ag granular films were prepared by potentiostatic deposition from a chloride-based electrolyte. Different Co(II)/Ag(I) ratios were tested to study the influence of the composition bath on the magnetotranport properties. All as-deposited samples showed GMR effect because both longitudinal and transverse magnetoresistances were negative in the whole field range. GMR values up to 5.85% were measured at room temperature. Electrochemical and structural techniques (XRD, TEM, and electron diffraction) as well as magnetoresistance measurements confirmed the heterogeneity of the deposits with a size distribution from superparamagnetic to ferromagnetic particles. Fcc-Ag and a mixture of hcp-Co and fcc-Co were present in the coatings. An analysis of the magnetotransport properties based on the decomposition of the total magnetoresistance into its ferromagnetic and superparamagnetic contributions revealed a high superparamagnetic contribution in all samples.

Measurement of the giant magnetoresistance effect in cobalt–silver magnetic nanostructures: nanoparticles

“…The developed method was shown to be successful as it was possible to measure the variation of the electrical resistance with the applied magnetic field in the prepared devices (figure 6(a)). As can be observed, values of a few tenths of an ohm were measured for the electrical resistance of the deposited nanoparticles, values which are of the same order of magnitude as those previously obtained in Co-Ag thin films [32,33]. This result indicates that a conducting path exists among the nanoparticles after their deposition on the glass substrate.…”

Measurement of the Giant Magnetoresistance Effect in Cobalt–Silver Magnetic Nanostructures: Nanowires

“…A clear dependence of the MR on the nanowire's cobalt content was also observed (Figure B). The same general trend than that previously observed in Co–Ag granular films is obtained: GMR values increased with the ferromagnetic metal content up to a maximum and then dropped off at higher cobalt contents, this variation being attributed to the modification of parameters that governs GMR. , The maximum MR value measured at room temperature was 0.5%. It is also important to mention that the values obtained here are higher than the values reported in the unique work dealing with the GMR of granular Co–Ag nanowires (0.2%), which indicates that more progress can be made.…”

“…This indicates that the relative weight of the superparamagnetic contribution (% SPM) is approximately 100%, which is in accordance with the only presence of superparamagnetic particles. On the other hand, the calculated % SPM in Co–Ag nanowires is higher than that observed in Co–Ag granular films in which % SPM was around 90%, , probably due to the restricted geometry of the pores.…”

Temperature dependence of GMR and effect of annealing on electrodeposited Co–Ag granular films

“…4C). The difference would be related to the smaller grain size detected in the as-deposited state of pulse deposited films if compare with potentiostatic films [10]. Independently of the electrochemical technique, the reason for such sudden decrease could be attributed to a notable increase in the cobalt granule size after the thermal treatment as complete phase separation between cobalt and silver exists in the asdeposited state.…”

“…The electrodeposition of Co-Ag granular films from a chloridebased electrolyte has been recently studied in our research group [9,10]. Cobalt-silver heterogeneous films with GMR were prepared by two different electrochemical techniques, chronoamperometry and pulse deposition, and from electrolytes containing different Co(II) concentrations.…”