Abstract
Here, an artificial spin ice lattice is introduced that exhibits unique Ising and non-Ising behavior under specific field switching protocols because of the inclusion of coupled nanomagnets into the unit cell. In the Ising regime, a magnetic switching mechanism that generates a uni- or bimodal distribution of states dependent on the alignment of the field is demonstrated with respect to the lattice unit cell. In addition, a method for generating a plethora of randomly distributed energy states across the lattice, consisting of Ising and Landau states, is investigated through magnetic force microscopy and micromagnetic modeling. It is demonstrated that the dispersed energy distribution across the lattice is a result of the intrinsic design and can be finely tuned through control of the incident angle of a critical field. The present manuscript explores a complex frustrated environment beyond the 16-vertex Ising model for the development of novel logic-based technologies.
Highlights
An artificial spin ice lattice is introduced that exhibits unique Ising and and synthetic environments as it possesses non-Ising behavior under specific field switching protocols because of the ground state residual entropy.[1,2,3,4] Artifiinclusion of coupled nanomagnets into the unit cell
Two modal magnetic states are exhibited in Figure 1ai,aii by magnetic force microscopy (MFM) images at remanence after applied field (B) along the yand x-axis, respectively
A violation of the ice rules has been demonstrated in artificial spin ice (ASI) lattices where Ising states break down into Landau states (LS) in response to a perturbing field protocol
Summary
The atomic force micrograph in Figure 1ai (inset) introduces the novel ASI lattice design. Two modal magnetic states are exhibited in Figure 1ai,aii by MFM images at remanence after applied field (B) along the yand x-axis, respectively. The greater dipole–dipole coupling between neighboring NIs results in an additional step in the energy progression where the full multitude of states shown in Figure 2b are observed (Figure 3biii) At the field increment, LSs are pushed out and the NIs return to an Ising ground state (Figure 3civ) This signals that the presence of the parallel nanomagnets in the QH-ASI lattice causes a deviation from the expected mean-field theory for LS generation within this field protocol, resulting in the MM configuration. This favorable LS formation and ice-rule violation may apply to other ASI lattices consisting of coupled parallel NIs such as the quadrupolar or trident ASI.[30,31,32,40]
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