Ac magnetic susceptibility of a molecular magnet submonolayer directly patterned onto a microSQUID sensor

TL;DR

This study demonstrates a method to enhance microSQUID sensitivity by integrating ferritin-based CoO nanoparticle monolayers, enabling precise ac susceptibility measurements of molecular magnets at ultra-low temperatures.

Contribution

It introduces a novel integration technique using Dip Pen Nanolithography to directly pattern molecular magnets onto microSQUID sensors, significantly improving sensitivity.

Findings

Achieved 100-fold increase in flux coupling and sensitivity.

Successfully measured ac susceptibility of molecular arrays at 13 mK.

Enabled characterization of 2D single molecule magnet arrays across various temperatures.

Abstract

We report the controlled integration, via Dip Pen Nanolithography, of monolayer dots of ferritin-based CoO nanoparticles (12 Bohr magnetons) into the most sensitive areas of a microSQUID sensor. The nearly optimum flux coupling between these nanomagnets and the microSQUID improves the achievable sensitivity by a factor 100, enabling us to measure the linear susceptibility of the molecular array down to very low temperatures (13 mK). This method opens the possibility of applying ac susceptibility experiments to characterize two-dimensional arrays of single molecule magnets within a wide range of temperatures and frequencies.