Exceptional Magnetomechanical Response of Glass-coated Amorphous Microwires

Abstract

The interesting magnetic behavior of chemically resistant and biologically inert glass-coated amorphous magnetic microwires has been of enduring interest since the mid-1980’s. However, their response under different mechanical loading conditions, of great interest for numerous sensor applications, has not been thoroughly explored. Here we present data connecting the magnetoelastic response of glass-coated amorphous ferromagnetic microwires with mechanical loading, revealing an exceptional magnetomechanical response. A selection of amorphous glass-coated Fe73Si11B13Nb3 microwire samples (100-110 μm outer diameter, 4 cm in length) were evenly covered with a thin layer of electrically conducting silver paint (Coating 1), electrically insulating nitrocellulose (Coating 2), or were left uncoated. The magnetomechanical response (resonant frequency and amplitude) of the wires was probed in the frequency range 30-100 kHz using a wireless pickup coil set-up of fixed 1.5 V voltage and a modulated current. It was found that the microwire resonant frequency systematically decreased on the order of ~3 kHz/mg, Fig. 1(a), independent of coating type, Fig. 1(b). These data confirm a shift in the magnetoelastic resonant frequency response of microwires that is approximately 100 times greater than that reported for Metglass amorphous magnetic ribbons (ref = Grimes et al.). These findings quantify the lower detection limits of mass loading in glass-coated amorphous magnetic microwires, where microgram differences in mass can be detected wirelessly and with no applied bias field. This exceptional responsiveness to mass loading, along with their small diameter, highlights the promise of magnetic microwires for a variety of sensor applications, including as biosensors, for civil infrastructure monitoring, and for anti-counterfeit measures. Acknowledgements – Fulbright España, I-Link A20074 (CSIC), Spanish Ministry of Science and Innovation RTI2018-095856-B-C21 and Comunidad de Madrid NANOMAGCOST S2018/NMT-4321