Realization of Rectangular Artificial Spin Ice and Direct Observation of High Energy Topology


Abstract in English

In this letter, we have constructed and experimentally investigated frustrated arrays of dipoles forming two-dimensional artificial spin ices with different lattice parameters (rectangular arrays with horizontal and vertical lattice spacings denoted by $a$ and $b$ respectively). Arrays with three different ratios $gamma =a/b = sqrt{2}$, $sqrt{3}$ and $sqrt{4}$ are studied. Theoretical calculations of low-energy demagnetized configurations for these same parameters are also presented. Experimental data for demagnetized samples confirm most of the theoretical results. However, the highest energy topology (doubly-charged monopoles) does not emerge in our theoretical model, while they are seen in experiments for large enough $gamma$. Our results also insinuate that magnetic monopoles may be almost free in rectangular lattices with a critical ratio $gamma = gamma_{c} = sqrt{3}$, supporting previous theoretical predictions.

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