Project A9 - Surface Acoustic Wave Magnetic Field Sensors
As part of the research in project A3 in the previous funding period, it was shown that surface acoustic wave (SAW) sensors using the ΔE-effect can be used for very sensitive, broadband magnetic field sensing. These sensors are based on a patented approach using shear horizontal acoustic surface waves that are guided by a fused silica layer (Love waves) with an amorphous magnetostrictive FeCoSiB thin film on top. The velocity of these waves follows the magnetoelastic-induced changes of the shear modulus according to the magnetic field present. The delay line operation of the SAW sensor translates these changes into a phase shift. With an extremely low magnetic noise level of approximately 70 pT/Hz1/2 at 10 Hz, a bandwidth of 50 kHz and a dynamic range of 120 dB, this magnetic field sensor system shows outstanding characteristics. In addition to piezoelectric bulk crystals, polycrystalline thin-film AlScN on a silicon substrate will be investigated as a possible alternative, since its electro-acoustic coupling coefficient is clearly superior, especially in the high frequency domain.
A main objective is to derive a comprehensive model for the sensitivity and the noise of magnetic field SAW sensors. This work will be performed in close collaboration with A1 on the magnetostrictive film, with project A8 on modelling of design parameters as well as of the acoustic wave propagation, with project A10 on magnetic noise modelling and characterization, and with project B1 on the overall noise models. The major questions will include the concept and realization of the magnetostrictive component and investigations on the frequency, which is of course not independent from the magnetostrictive material of choice.
Besides this general objective, the following sub-objectives will guide the corresponding work packages, while the major results will be included in the signal-to-noise model:
- For single crystalline SAW sensors, the choice of the piezoelectric single crystals and the material and layout of the guiding layer will be investigated as important parameters for the sensors´ performance;
- for thin film SAW sensors, the acoustic mode and the layout of the sensor will be investigated and compared to our reference single crystalline SAW sensors; and
- for phononic crystals, acoustic band gaps with defect-induced transmission windows as well as the micromagnetic fine-structure of the individual magnetic lattice elements will be investigated.
Involved Researchers
Person | Role | |
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Prof. Dr. Eckhard Quandt Materials Science Inorganic Functional Materials |
Project lead | |
Dr. Fabian Lofink Microsystem Technology Fraunhofer Institute |
Project lead | |
M.Sc. Jana Meyer Microsystem Technology Fraunhofer Institute |
Doctoral researcher | |
M.Sc. Felix Weisheit Materials Science Multicomponent Materials |
Doctoral researcher |
Role within the Collaborative Research Centre
The CRC 1261 spans a wide range of projects: from materials research to sensor concepts to signal processing and finally to applications. Because this project deals with one of the sensor concepts, it is fully integrated within this research chain and we will have intense collaborations with materials research, sensor systems, and even with applications, especially with the transfer project. The last collaboration includes mainly the support of T1 in its measurements using SAW sensors for the localization of deep brain stimulation (DBS) and using the derived data and information for further improvement of the sensors for this application. In particular, the following close collaborations with other projects are planned:
Collaborations | |
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A1 (Magnetostrictive Multilayers for Magnetoelectric Sensors) | Application of advanced magnetic multilayers to SAW sensors. |
A6 (Microstructure and Structural Change of Magnetoelectric and Piezotronic Sensors) | Chemical and structural analysis of AlScN. |
A8 (Modelling of Magnetoelectric Sensors) | Modelling of SAW sensor parameters and designs as well as of acoustic superlattices. |
A10 (Magnetic Noise of Magnetoelectric Sensors) | Numerical studies on noise and in operando time-resolved MOKE measurements. |
B1 (Sensor Noise Performance and Analogue System Design) | Analog electronics, noise floor characterization, LOD measurements, chopper approach. |
B2 (Digital Signal Processing) | Setup of specifically tailored read-out schemes for SAW sensors. |
B7 (3D-Imaging of Magnetically Labelled Cells) | SAW sensors for MSPM and magnetorelaxometry experiments. |
T1 (Transfer project – Individualized Deep Brain Stimulation) | DBS measurements using SAW sensors. |
Z1 (MEMS Magnetoelectric Sensor Fabrication) | Support in SAW sensor fabrication. |
Z2 (Magnetoelectric Sensor Characterization) | Support with sensor characterization and DBS measurements. |
Project-related Publications
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