Artificial spin ice materials consist of arrays of nanomagnets arranged in such a way that their magnetic moments are “frustrated”. This means that they do not have a stable ground state where all of the magnetic moments, or spins, are aligned. The term spin ice is used, because the magnetic spins are arranged similarly to the orientation of hydrogen in water ice molecules. Spin ice has potential new applications in computation and data storage.
Recent research has made advances in where and how magnetic domains change in spin ice arrays using astroid clocking. The term “astroid clocking” gets its name from the astroid shape of the switching field-curve of a single nanomagnet, as described by the Stoner-Wohlfarth model. By applying separate field pulses along different directions relative to the astroid shapes, nanomagnets can be selectively switched, or clocked. Astroid clocking allows for a discrete, step-wise, and gradual dynamic process where domains can be grown or reversed at will.
The novel work was reported by Johannes Jensen, Anders Strømberg, Ida Breivik, Arthur Penty, Miguel Angel Niño, Muhammad Waqas Khaliq, Michael Foerster, Gunnar Tufte Erik Folven in a collaborative effort from the Norwegian University of Science and Technology (NTNU) and the ALBA Synchrotron.
The work was performed in part using an STS-Elionix ELS-G100 electron beam lithography system in the shared user facilities of the NTNU NanoLab.
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Image (courtesy Anders Strømberg): Scanning electron image of an artificial spin ice consisting of an array of nanomagnets.