Barrera, A.; Fourneau, E.; Pirottin, T.; Marcano, L.; Abrudan, R.; Huang, R.; Balcells, L.; Orue, I.; Fdez-Gubieda, M.L.; Villanueva, D.; Gubieda, A.G.; Chang, L.; Vanderheyden, B.; Harrison, R.J.; Silhanek, A.; Palau, A.; Valencia, S.: Extending Field Limits in Nanoscale Magnetic Imaging With Metamaterial-Inspired Magnetic Flux Concentrators. Small early view (2026), p. e00073
10.1002/smll.202600073
Open Accesn Version
Abstract:
Many nanoscale magnetic imaging techniques are constrained by the maximum magnetic field that can be applied duringmeasurements, due to geometrical limitations or interactions with the probe or the detected signal (e.g., electrons). Here, it isdemonstrated that sample-integrated metamaterial-inspired magnetic flux concentrators (MFCs) locally amplify magnetic fields,allowing observation of magnetization processes beyond instrumental limits. Micrometer-sized MFCs fabricated directly on thesamples are tested in photoemission electron microscopy experiments employing X-ray magnetic circular dichroism as magneticcontrast mechanism. At low applied fields, substantial amplification factors enable observation of magnetization reversal in a chainof magnetite nanoparticles synthesized by magnetotactic bacteria at an applied field of 8 mT, substantially smaller than the ∼50 mTpredicted by simulations in the absence of MFCs. At higher fields, the field enhancement extends the accessible field range by afactor of five, enabling for the first time, imaging of the field-dependent magnetic domain structure evolution of an isolated giantmagnetofossil. Finally, we show how MFC geometry and material parameters can be tuned to optimize performance consideringsample and experimental constraints, providing a tunable and broadly applicable strategy for extending the accessible field rangein a wide variety of nanoscale magnetic imaging techniques