PhD defence Rossi on scanning probe microscopy and dilatometry in high magnetic fields
Lisa Rossi dedicated half of her time at the HFML to designing and building new instruments. Her high–field scanning tunneling microscope (STM) and high–field scanning probe microscope (HF–SPM) can be used to measure in high fields (above 30 Tesla) and in extreme cold ( about -270 C°). Both instruments required an extremely rigid design and a good vibrational damping system. Plus they had to be compact enough to fit inside the 32 mm diameter bore of the magnets. Lisa: “It has been a big puzzle. But it was worth it, as we can have a much better look at what happens with matter in high fields now.”
The other part of her thesis was devoted to experimental work on the antiferromagnetic spinel compound CdCr2O4, which is shown to exhibit novel phenomena related to magnetic frustration. Lisa:“This was a surprise, we didn’t expect this and at first we weren’t sure what we were seeing.”
These results can be applied across a broad range of spinel and pyrochlore magnets, and potentially other frustrated magnets. Lisa demonstrated that is possible to perform local polarization measurements in high magnetic field, using electrostatic force microscopy (EF) performed with the HF–SPM, allowing to measure polarization on a nanometer length scale, within a single domain. This new method for measuring polarization can provide a new tool for studying multiferroic samples with nano- and meso–scale inhomogeneities, such as multiferroic domain walls.
Last November, Lisa started working as a Physic design engineer at Nearfield Instruments, a company that produces high throughput scanning probe microscopes for semiconductor metrology. Her job is to design and develop experiments for early integration tests and perform research for the next machine generation. Pretty much in line with her PhD at HFML. "That was also the part that I liked most. I am a practical person and I always like to design, build and test things."
Lisa Rossi defended her doctoral thesis on Thursday 16 April. Due to strict coronavirus measures her promotion took place online via video conferencing. Less impressive than the Aula, but nevertheless her defense was successful.
Supervisor: prof. dr. N.E. Hussey
Co-supervisor: dr. B. Bryant