Invited Talk: Fundamental Magnetic Interactions in Patterned Nanostructures: Simulation, Fabrication and High-Resolution Microscopy

Thank you to the organizers of  the 2013 MXLS Workshop "New Opportunities for Magnetic Dynamics and Materials at NSLS-II and MAX-IV” for the invited talk.

Fundamental Magnetic Interactions in Patterned Nanostructures: Simulation, Fabrication and High-Resolution Microscopy

Through the use of complimentary multi-technique experimental approaches, investigations of fundamental magnetic interactions, such as magnetostatic, direct exchange, and indirect exchange, in nanomagnetic structures perturbed by static and high frequency excitation, are presented.

Suggestions of using dipolar coupled single domain patterned nanomagnets for applications such as logic, has demonstrated the potential for low-power room temperature operation. The fundamental evolution of reaching desired states can be described as an energy minimization process, where elements exhibit preferential magnetization axes due to engineered shape anisotropies, and local energy minima are reached utilizing external stimuli and strong magnetostatic interactions. Magnetic Force Microscopy (MFM) was implemented in conjunction with NIST’s micromagnetic framework OOMMF, in order to detail the energies associated with different local ground states of coupled nanomangets. The kink energy and magnetic frustrations in ferromagnetic and anti-ferromagnetic ordered elements in various directional applied fields will also be discussed.

Dipolar interactions produce long range force fields but stronger yet are the quantum mechanical short range exchange interactions of neighboring spins. The competing energies of exchange interactions in domain walls and magnetic flux due to surface charges at boundaries can lead to interesting topological charges in room temperature nanomagnetic systems. In a properly engineered nanodisk, magnetic vortices appear, with two degrees of freedom (chirality and polarity), four degenerate states, and exhibit radial symmetry at equilibrium. Utilizing ferromagnetic resonance, transmission electron microscopy, and x-ray transmission microscopy, details of competing direct exchange, demagnetization, indirect exchange energies in magnetic vortex systems are investigated through the observation of core deformation in static fields. The use of high frequency field excitations applied in-situ in TEM to dual vortex core indirect exchange coupled nanodisk heterostructues and the frequency response probed through the time averaged orbital amplitude are also presented.