R. Varga
RVmagnetics, a.s.,
Slovakia
Keywords: sensors, contactless measurement, magnetic bistability, magnetic microwire
Summary:
Glass-covered microwires are composite materials that consist of metallic nucleus (diameter 1–50 μm) and glass coating (thickness 2–20 μm) [1]. Their size and easy production of large amount (kilometers) in a short time (10 min) leads to their utilization as a miniaturized sensor that can be embedded inside of studied materials or objects [2]. Apart from easy production and size, glass-coated microwires shows unique magnetic properties that allow their utilization in noisy environment symmetry, while their magnetic nature allows for contactless sensing. Additionally, glass coating provides insulation from chemically aggressive environment and provides biocompatibility. As a result of complex stress distribution induced during production, microwires with positive magnetostrictions show peculiar magnetization state that shows magnetic bistability. The magnetic state of such microwires is characterized by two saturated states with positive or negative saturation magnetization. Change of magnetic state runs through the depinning and subsequent propagation of single domain wall along the entire microwire in a single Barkhausen jump at the so-called switching field Hsw. The switching field depends on magnetic field, temperature, mechanical stress, or radiation. Therefore, bistable microwires can be employed for production of contactless passive sensing elements [3]. Additionally, magnetic bistability allows for separation of magnetic field and temperature/stress contribution which results in magnetic sensor of temperature/stress, which is not sensitive to magnetic fields. Within this contribution we will describe all advantages and disadvantages of applications based on magnetically bistable microwire. Different applications of contactless sensors for temperature, stress, magnetic field, electrical current, position, humidity, etc. will be presented. Simple cheap electronics will be introduced that allows for construction of unique passive contactless sensors in medicine, engineering, IT, automotive, and many other areas. References: [1] M. Vazquez, Advanced magnetic microwires, in: H. Kronmuller, S.S.P. Parkin (Eds.), Handbook of Magnetism and Advanced Magnetic Materials, Wiley, Chichester, England, (2007), 2193–2226. [2] A. Zhukov, V. Zhukova, Magnetic Properties and Applications of Ferromagnetic Microwires With Amorphous and Nanocrystalline Structure, Nova Science Publishers, New York, (2009). [3] R. Jurc, L. Frolova, D. Kozejova, L. Fecova, M. Hennel, L. Galdun, K. Richter, J. Gamcova, P. Ibarra, R. Hudak, I. Sulla, D. Mudronova, J. Galik, R. Sabol, T. Ryba, L. Hvizdos, P. Klein, Z. Vargova, R. Varga., Sensoric application of glass-coated magnetic microwires, (2020) Magnetic Nano- and Microwires: Design, Synthesis, Properties and Applications, 569.