Quantum sensing, defined as the use of a qubit system to measure environmental parameters, has been realized in a variety of physical platforms from alkali vapor cells to superconducting circuits. The nitrogen-vacancy (NV) defect in diamond is one realization amongst many and while there exist systems with better raw sensitivity metrics, the combination of room temperature operability, biocompatibility, and exceptional spatial resolution potentially enables the study of chemical and biological phenomena inaccessible to other platforms. In this seminar, I will show different examples of using quantum sensing microscopy (QSM) to probe nanoscale magnetic phenomena in different bio and solid-state materials. Then, I will focus on recent QSM measurements performed on individual Fe(Htrz)2(trz)](BF4)] (Fe triazole) spin-crossover (SCO) nano-rods of size varying from 20 to 1000 nm. Fe triazole SCO complexes exhibit thermal switching between low spin (LS) and high spin (HS) states which are applicable in thermal sensors and molecular switches. While the bulk magnetic properties of Fe triazole molecules are widely studied by bulk magnetometry techniques their properties at the individual level are missing. The magnetic field patterns produced by the nanoparticles/nanorods are imaged by NV-QSM as a function of applied magnetic field and temperature. We found that in most of the nanorods the LS state is slightly paramagnetic, explained by the surface oxidation and/or the greater Fe(III) presence along the nanorods’ edges. NV measurements on the Fe-triazole LS state nanoparticle clusters revealed both diamagnetic and paramagnetic behavior. Our results highlight the potential of NV-QSM to study the magnetic properties of spin crossover molecules and molecular magnets.
Speaker: Abdelghani Laraoui
