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AQP -seminaari: Magnetic Field Sensing through Surface Waves

Aalto Quantum Physics -seminaari (Nanotalo).
Puhuja: Harshad Mishra ( Institut Jean Lamour - CNRS)

The prominence by virtue of their simultaneous sensing as well as actuation ability. Not only do they reduce the complexity but also impart a multifunctionality to the device. Magnetic sensors available today in the market may be classified as high field, medium field or low field devices depending on the range of field in which they measure (~mT, ~µT and ~nT respectively). However, almost all of these devices operate with a complex mechanism while simultaneously being externally powered as well as expensive. Thus there arises a deep need to develop a magnetic sensor that overcomes the challenges. This research work focused on the development of surface acoustic wave (SAW) sensors for the detection of magnetic field.

Owing to the possibility of wireless interrogation, SAW devices of the resonator configuration have been considered in this study. In the magnetic surface acoustic wave (MSAW) devices, it is known that the resonance frequency is sensitive to external magnetic field, primarily through both static effects related to the field-induced magnetization changes, and the magnetoelastic dynamic effects related to the acoustic wave. In our work, we have attempted to study and relate the magneto-acoustic responses of the MSAW devices to its magnetic anisotropy. On a more generalized perspective, we have investigated the possibility to engineer the magneto-acoustic response, and thereby the sensitivity of the device, by optimizing the magnetic properties as well as thermal effects on the elastic and magnetic properties, to suit specific requirements.

In my talk, I will first discuss the basics of the sensing through surface acoustic waves and the physics behind the sensing of magnetic field. I will then discuss a SAW based magnetic sensor developed using LiNbO3 as the substrate and multi-layered [TbCo2/FeCo] as the electrode and sensitive material, and highlight the need for the shape effects in magnetism in engineering the device for optimum response. Subsequently, we address the concerns arising from the effects of temperature and I will present to you a temperature compensated SAW device developed for magnetic field sensing based on Love waves. Finally, I shall address concerns related to the effect of temperature on magnetic anisotropy and will present to you a novel proof-of-concept multi-sensory device. Here, we combine our understandings of the shape effects of magnetism with the temperature compensated structure. The developed sensor is therefore immune to the effects of temperature on the resonance frequency as well as the magnetic anisotropy.

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