| dc.description.abstract | Advanced magnetic materials have played an important role in, and continue to pave
the way for, innovative technological advancements. Modern day computers, sensors,
and biomedicine would not be possible without the use of such materials. Assemblies
of magnetic metamaterials, comprised of a complex microscopic structure, presents a
new and promising opportunity to specifically tailor nearly all magnetic properties of a
material. This thesis presents an in-depth, multipronged attempt at understanding and
creating specific instances of such magnetic materials with emergent ensemble properties.
Micromagnetic modeling of stable (and ground) states of such structures have been
carried out. The simulation results are used to predict and verify the observation of
physical instances of corresponding structures. Emergent superferromagnetic and super-
antiferromagnetic behavior was found for structures of different lattice geometries, in
two-dimensional, patterned permalloy thin film. Of note is the long-range order of the
superferromagnetic states and the indication that certain structures can be coerced into
both superferromagnetic and superantiferromagnetic metastable states.
Physical structures of ordered nanomagnets were designed and later fabricated at
NTNU NanoLab s cleanroom facilities. The samples were inspected through the use of
magnetic force microscopy at cryogenic temperatures and subjected to varying applied
magnetic fields in order to classify the structures behavior. A stable, physical, super-
ferromagnetic state was clearly observed and classified for triangular lattice geometries.
Similar states were found for square lattice geometries, in addition to indication of the
presence of a switchable superantiferromagnetic state. Additionally, several auxiliary
results were obtained and auspicious suggestions for further work is provided. | |
