The work performed within WP1 consisted on the development and optimisation of the epitaxy process and the deposition of ultralow damping YIG films by pulsed laser deposition (PLD). This was performed in tight collaboration with the PLD manufacturer, Solmates B.V. (Enschede, The Netherlands). This goal was successfully achieved within the targeted specifications (thickness range 50–100 nm; Gilbert damping α < 10-3). The characterization methods include X-ray diffraction, transmission electron microscopy and ferromagnetic resonance (FMR). Particularly, the FMR measurements enabled the knowledge transfer from the secondment group (U Paris Sud), with recognised longstanding expertise with FMR, to the host institution (IMEC).
The work developed in the scope of WP2 comprised the development of magnetoelectric (ME) transducers. These devices act as generators, detectors, and training mechanism of SWs, and promise the best scalability and highest energy efficiency of all approaches (e.g. with respect to microwave antennae). The work performed in NeuroMag was a significant step towards the understanding of ME transducers. Particularly, the significant material and fundamental physics challenges still hampering this approach. The material challenges concern the deposition of epitaxial YIG films with a conductive bottom electrode. Furthermore, the deposition of the piezoelectric material Pb(ZrxTi1-x)O3 (PZT) on YIG also depicted a strong impact on the magnetic properties of the YIG film. As for the more fundamental challenge, micromagnetic simulations have shown a very complex magnetization dynamics is generated by the magnetoelectric mechanism. This feature averages out the detected signal preventing the SW detection. These findings will help the ME community to find alternative approaches and geometries that will enable the fabrication of efficient and scalable SW transducers.
The learnings of WP1 and WP2 were applied to the device proof of concept of WP3. The YIG films (WP1) were used as SW medium, and a new strategy was defined using antennae with steps, to simulate the intended effect of ME cells (WP2) as a training mechanism (local magnetic fields). The device functionality could be demonstrated (particularly bidirectionality and training). Furthermore, the collaboration with U Paris Sud allowed the researcher to become an expert on SW spectroscopy and to perform the full knowledge transfer to the host laboratory. In fact, an RF electrical measurement setup incorporating an applied magnetic field was built at IMEC. Both the hardware and software development were performed in the scope of NeuroMag.
