Magnetotransport Properties of Co-Au Granular Alloys

Abstract

Abstract-A series of Cox-Au1-x granular alloys was grown using pulsed-current electrodeposition on polyimide substrates. The relationship between the giant magnetoresistance effect, saturation magnetization, and grain size was examined as the deposition current density and annealing temperatures were changed. A maximum magnetoresistance (MR) ratio of 4.5 % was obtained. The magnetization and ferromagnetic grain size of the as-deposited and annealed alloy films were examined against the deposition current density. The saturation magnetization decreased as the composition of Au was increased for both the alloys deposited at the current densities of 1 and 5 mA/cm2. The total magnetic moment further decreased on annealing. The grain size is found to be highly influenced by both the deposition current density and temperature. A low temperature magnetization measurement suggested that the ferromagnetic grain size decreases with increase in current densities. For the annealed samples, the ferromagnetic grain sizes were found to be dispersed in the Au matrix with different diameters. The decrease in magnetic moments with annealing is correlated with the grain size of the Co and its distribution in the gold matrix. The MR ratio increased with the increase in the deposition current density as a result of the formation of smaller grain size at higher deposition current densities.

Experimental Correlation between Nonlinear Optical and Magnetotransport Properties Observed in Au-Co Thin Films

“…We begin our analysis by noting that in such segregated nanocomposite systems, small single-domain magnetic clusters can exist where the sizes of the ferromagnetic domains remain unchanged and hence the external field only rotates the magnetic axes of the clusters towards complete alignment; therefore, the size of the magnetoresistive effect depends on the number and size of magnetic clusters within the probed volume [12]. In our case, the maximum in magnetoresistance near 35% Co content corresponds to the optimal cluster size (typical grain radius 1.4 nm) [10] and intercluster separation for this system [13,14], consistent with other reports [15]. Low magnetoresistance values for sample composition below 30% Co content are consistent with a relatively low concentration of magnetic clusters, thus leading to fewer interfacial scattering sites.…”

Physical Properties of Film Alloys Based on Ferromagnetic and Noble Metals (review). ІІ. Film Materials Based on Co and Ag or Au

“…An analogy with the analysis of the survey results (Tables 1 and 2) we realized the same generalization to film systems based on Au and Co (Table 4) based studies [32][33][34][37][38][39][40][41][42]. The results is uniquely indicated that GMR value not significantly dependent on the structural state -multilayer or granulated film based s.s.…”

“…Granules size ranged from 1.5-3 to 10 nm, which substantially affect the value of GMR. Conclusion regarding granular state was later confirmed in works [10,34].…”

Ferromagnetic Multilayers: Magnetoresistance, Magnetic Anisotropy, and Beyond

“…In the presence of an externally applied H field of 10 kOe, the Pulsed-current deposited multilayers of Fe/Cr showed room temperature MR of 8% [61], whereas multilayers of Co/Ag showed a MR of 9.1% [56]. Co/Cu on the other hand showed 4.1% [40] in the presence of 1 kOe and Co/Au showed 4.5% [62] in the presence of 20 kOe. Note is to be made that these results are either comparable to or better than those exhibited by vapor deposited Fe/Cr, Co/Ag, Co/Cu, and Co/Au multilayers.…”