Boosting the Tunable Microwave Scattering Signature of Sensing Array Platforms Consisting of Amorphous Ferromagnetic Fe2.25Co72.75Si10B15 Microwires and Its Amplification by Intercalating Cu Microwires.

Diego Archilla,Jesús López-Sánchez,Elena Navarro,Antonio Hernando,Pilar Marín

doi:10.3390/nano11040920

Abstract

The following work addresses new configurations of sensing array platforms that are composed of Co-based amorphous ferromagnetic microwires (MWs) to obtain an enhanced modulation of the microwave scattering effects through the application of low strength DC or AC magnetic fields. An amorphous MW is an ultrasoft ferromagnetic material (coercivity ~0.2 Oe) with a circumferential magnetic anisotropy that provides a high surface sensitivity when it is subjected to an external magnetic field. Firstly, microwave scattering experiments are performed as a function of the length and number of MWs placed parallel to each other forming an array. Subsequently, three array configurations are designed, achieving high S21 scattering coefficients up to about −50 dB. The influence of DC and AC magnetic fields on S21 has been analyzed in frequency and time domains representation, respectively. In addition, the MWs sensing array has been overlapped by polymeric surfaces and the variations of their micrometric thicknesses also cause strong changes in the S21 amplitude with displacements in the frequency that are associated to the maximum scattering behavior. Finally, a new concept for amplifying microwave scattering is provided by intercalating Cu MWs into the linear Co-based arrays. The designed mixed system that is composed by Co-based and Cu MWs exhibits a higher S21 coefficient when compared to a single Co-based MW system because of higher electrical conductivity of Cu. However, the ability to modulate the resulting electromagnetic scattering is conferred by the giant magneto-impedance (GMI) effects coming from properties of the ultrasoft amorphous MWs. The mixed array platform covers a wide range of sensor applications, demonstrating the feasibility of tuning the S21 amplitude over a wide scattering range by applying AC or DC magnetic fields and tuning the resonant frequency position according to the polymeric slab thickness.

Highlights

Exploring new physicochemical phenomena that arise, when materials are confined to the nanoscale, as surface energy becomes relevant or dominates the volume energy, is one of the fundamental strengths of the multifunctional applied materials science
Nanomaterials 2021, 11, 920 that dazzle by their high versatility and variability in their properties, when they are subjected to an external stimulus [1,2,3,4,5,6,7]
For the electromagnetic microwave technology, multifunctional materials with tunable properties by external stimuli are essential to progression in the field of sensing applications [4,8,9], microwave shielding systems [7,10,11,12], wireless communication [13,14], antenna engineering [15,16], hyperthermia [17], and biomedical engineering [18,19,20]

Summary

Introduction

Exploring new physicochemical phenomena that arise, when materials are confined to the nanoscale, as surface energy becomes relevant or dominates the volume energy, is one of the fundamental strengths of the multifunctional applied materials science. Nanomaterials 2021, 11, 920 that dazzle by their high versatility and variability in their properties, when they are subjected to an external stimulus (i.e., an applied electric and/or magnetic field, mechanical stresses, temperature, and a gas exposure) [1,2,3,4,5,6,7]. The crossed control of the electromagnetic properties is appealing for advanced performances, involving the ability of modulating the electrical response by means of a magnetic field and . Such cross-modulation requires materials with strong magneto-electric coupling [21]

Methods

Results

Conclusion