## 3 Results and Discussion
### Evolution of the Microwave Scattering Properties in Co-Based MWs Linear Arrays
As the electrical conductivity of the MW is higher, its scattered  
\[E_{t}=\xi\left(\mathbf{H}_{t}\times\mathbf{n}_{r}\right) \tag{3}\]0 AC magnetic field experiments performed in the sensor array platform configuration 2 of Co-based MWs: (**a**) the \(\Delta S_{21}\) trends with the overlapped thickness placed on the top of the Co-based MWs at fixed frequencies ranged from 2.00 GHz to 2.40 GHz; (**b**) time-resolved modulation of the scattering coefficient \(\Delta S_{21}\) due to an AC-bias magnetic field (\(H_{\mathrm{AC}}\) = 17 Oe,\(f_{\mathrm{AC}}\) = 10 Hz) and a fixed electromagnetic microwave frequency of 2.10 GHz as a function of the thickness of polymeric slabs (\(t\)) overlapped from 0 to 6000 \(\upmu\)m.  
amplitude is larger, because the electric current is higher. In this sense, the present Co-based MWs show a value of \(\sigma_{\text{Co\,MW}}\sim 2.10^{7}\) S m\({}^{-1}\), and it can be surpassed by some non-magnetic metallic elements, such as Cu. Therefore, it would be interesting to design combined Co-based and Cu MWs arrays to evaluate their response in the microwave electromagnetic scattering and, subsequently, to obtain their modulation through the application of DC or AC magnetic fields. For this purpose, Cu MWs with a diameter of \(\sim\)100 \(\upmu\)m are chosen, which correspond to a \(\sigma_{\text{Cu\,MW}}\sim 6.10^{7}\) S m\({}^{-1}\) (Figure 8). Configuration 2 is chosen as an example of potential technological application to exploit the proposed approach to improve the amplitude of microwave scattering maintaining the ability to be modulated with DC magnetic fields. For this end, array sensing platforms are fabricated to evaluate their microwave scattering properties while using Co-based MWs (Figure 8a1), Cu MWs (Figure 8a2), and a combination of alternating Co-based and Cu MWs (Figure 8a3). Under non-applied field conditions (Figure 8b), the resonant frequency \(f_{\text{min}}\) is located around \(\sim\)2.38 GHz for the three sensing array platforms (\(L=4\) cm) confirming the antenna character of the Co-based MWs. In contrast, the resonance amplitude increases dramatically from \(\sim\)\(-\)14.4 dB (Co-based MWs configuration) to \(\sim\)\(-\)26.2 dB (Cu MWs configuration). For the array combination of alternating Cu and Co-based MWs, a minimum amplitude of the \(S_{21}\) transmission coefficient is recorded with an intermediate value between the previous configurations of \(\sim\)\(-\)17.8 dB. However, the latter combination retains the advantage of being able to adjust the minimum amplitude through the application of relatively low strength magnetic fields due to the ultrasoft magnetic character of the Co-based MWs (Figure 8c1). In this line, Figure 8c2 shows the variation of the peak amplitude, when a DC magnetic field up to 17 Oe is progressively applied. For such a field, a minimum value of \(\sim\)\(-\)11.2 dB is recorded. By calculating the values of \(S_{21,\text{relative}}\) (Equation (6)), a linear decreasing trend is also detected, as happened  
\[E_{t}=\xi\left(\mathbf{H}_{t}\times\mathbf{n}_{r}\right) \tag{3}\]1 Influence of non-field and DC magnetic field conditions on the microwave scattering for the configuration 2: schematic illustration for sensing array platforms composed by (**a1**) Co-based MWs, (**a2**) Cu MWs, and (**a3**) a combination of Co-based and Cu intercalated MWs; (**b**) the \(S_{21}\) transmission coefficient obtained for the three cases under non-field conditions; (**c1**) the \(S_{21}\) transmission coefficient obtained under a DC magnetic field between 0 and 17 Oe for the combination of Cu and Co-based MWs arrays (combination (**a3**)), and (**c2**) \(S_{21,\text{relative}}\) value calculated for the combined system of Co-based and Cu MWs. The \(S_{21,\text{relative}}\) distribution of the combination (**a1**) with Co-based MWs is also added for comparison. with the Co-based ones (combination (a1) in Figure 8), but with a lower slope reaching a maximum variation of \(\sim\)40%.