Self-assembly of superparamagnetic nanoparticles used in MRI thermometry

Self-assembly of superparamagnetic nanoparticles has been a highly studied topic, both as an interesting problem and for a wide range of practical applications such as storage media and biomedical technologies [1]. During a recent study of superparamagnetic nanoparticles utilized as temperature sensitive contrast agents for Magnetic Resonance Imaging, we have found that synthesized superparamagnetic nanoparticles (mixed ferrite of 10 nm size) under no applied magnetic field form pentagonal rings. It has been shown theoretically that pentagonal rings are a minimal energy configuration for self-assembly of spherical magnetic nanoparticles [2]. In this work we analyze the effects of the local magnetic fields generated by these pentagonal structures on water proton nuclear magnetic relaxation. These results are important for further understanding of local magnetic fields generated by such assemblies and how they affect temperature dependent MRI imaging using magnetic nanoparticles as contrast agent.
[1] S. Mehdizadeh, et al, Proceedings of the National Academy of Sciences 112.14484 (2015)
[2] R. Messina et al. Phys. Rev. E. 89. 11202 (2014)