Magneto-Impedance in Co35Fe65/Cu/Co35Fe65 Single and Bi-layer Thin Films

Abstract

The magneto-impedance response in Co35Fe65/Cu/Co35Fe65 thin film magneto-impedance cells deposited by the thermal evaporation method has been studied with single and bilayer structures at the substrate temperature 300 K and 150 K. While the thin film deposited at 300 K has BCC structure, the amorphous character is dominant for 150 K deposited ones. Entire films show soft magnetic behavior with high saturation magnetization (MS) and low coercive field (HC). Bilayer thin film structure reveals higher magneto-impedance values than single-layer thin films. The relation between the magneto-impedance effect and layered structure is discussed in terms of structural growing mechanism and scattering effect. The highest magneto-impedance sensitivity (η) 37%/Oe is observed for the Co35Fe65/Cu/Co35Fe65 bilayer thin film. The HC and remanence ratio (MR/MS) values for single layer at 300 K, single and bilayer cells at 150 K are measured as 51, 158 and 253 Oe—0.48, 0.78, and 0.80, respectively. When η with the Soliton wave model is compared with the sample at room temperature, an increase of over 1700% is observed. The difference between the classical growing method at 300 K and the Soliton wave model at 150 K is the evidence of the logic of the work performed and its accuracy. The relatively high sensitivity is connected with interlayer usage and low temperature-smaller particle size in Soliton model growth. The observed findings are of practical importance to develop future technological magnetic sensor applications with high sensitivity.