Defense PhD Thesis

RNDr. Katarína Neilinger

IEE SAS, August 17, 2021,  11,00 a.m.

Abstract:
The presented work aims at the modification of commercial AFM cantilevers
to fabricate a micro-cantilever-based magnetic sensor. The sensor is used as a
sensitive magnetometer to study magnetic interaction between ferromagnetic
micro-objects prepared on it.
At first, we addressed a challenging task of electron-beam lithography performed on a commercial cantilever. We solved the problem of covering the free-standing cantilever
with resist using an auxiliary chip inserted below the cantilever. In this way, we quasi-planarized
the cantilever surface, which allowed us to use a standard spin-coating process.
Second, we present another method to prepare the magnetic structures on
a cantilever by a resist-less technique without the necessity of multistep
lithography patterning. We used the subtractive process, which employs a
focused-ion beam patterning of magnetic thin film deposited on the cantilever.
We designed and fabricated the dual-cantilever sensor to study the behavior
of the mutual magnetic interaction of ellipse-shaped permalloy structures
prepared on adjacent cantilever parts in changing external magnetic field. We
detected the changes in magnetic states of the ellipses by the phase shift
of the vibrating cantilever. This detection method provides a non-invasive
measurement that does not perturb the magnetic state of the inspected system.
Our observations were supported by additional magnetic force microscopy
experiments, micromagnetic simulations and numerical calculations.
Keywords: micro-cantilever magnetometry, EBL, FIB patterning, AFM cantilever,
micromagnetic simulations, permalloy microstructures.