Collective dynamics in magnetic nano-structures
Researchers at the Division of Solid-state Physics and the Division of Material Physics at Uppsala University have shown how the collective dynamics in a structure consisting of interacting magnetic nano-islands can be manipulated. Their findings are published in the scientific journal Scientific Reports
With the aid of modern nano-fabrication methods the researchers have imitated nature and created a 2D pattern of small stadium shaped magnetic islands. These small magnets have properties similar to those of magnetic atoms, exhibiting thermal fluctuations. The time and temperature dependence of the magnetization in a collective of magnetic islands has been studied, using a very sensitive custom build magnetometer, developed in Uppsala.
" One of the advantages of using such mangetic nano-islands instead of magnetic atoms, as our primary building blocks is that the magnetic properties of the islands can be tuned with precision, something otherwise very difficult. To have precise control of your building blocks helps tremendously when analyzing measurements," explains Vassilios Kapaklis, Associate Professor in material physics at Uppsala University.
A collective magnetic state is formed when these magnetic islands are allowed to interact and it is this state, which the researchers studied. The collective can exhibit emergent properties differing strongly compared to those of the single building blocks and that can be controlled by the geometrical placement of the building blocks.
"Out results show that magnetometry can be used to monitor the development of the magnetic collective in real time, while also offering the possibility to study the impact temperature has on this development," says Mikael Andersson, PhD student in solid state physics at Uppsala University.
The understanding of collective effects in magnetic nanostructures is crucial for realizing applications such as magnetic logical circuits, which have the advantage of not requiring power to preserve a desired logical state.
The work was done in collaboration with the Center for Functional Nanomaterials, Brookhaven National Laboratory in the USA.
The research was financed by the Swedish Research Council (VR), Knut and Alice Wallenbergs, the Göran Gustafsson Foundation and STINT.
Andersson et al. (2016) Thermally induced magnetic relaxation in square artificial spin ice, Scientific Reports, DOI:10.1038/ srep37097