Defect-induced monopole injection and manipulation in artificial spin ice

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Artificial spin ice (ASI) arrays exhibit emergent collective dynamics and writable magnetic order, making them suitable for probabilistic computing and reconfigurable magnonics.
• Geometric frustration in ASI lattices leads to the formation of topologically protected magnetic charges (emergent monopoles) upon macrospin flips.
• Controlling individual monopoles and their counter-monopoles in ASI arrays is challenging without affecting other excitations.

Purpose of the Study:

• To tailor the local magnetic order in a classic ASI lattice by introducing a ferromagnetic defect.
• To establish controllable injection and propagation sites for emergent magnetic monopoles.
• To enable fine control over macrospin inversion pathways for functional device realization.

Main Methods:

• Fabrication of lithographically defined ASI arrays with an integrated ferromagnetic defect exhibiting shape anisotropy.
• Magnetic characterization to identify nucleation fields for monopole formation at the defect site.
• Stimulation of monopole propagation through the ASI lattice via the defect site.

Main Results:

• Introduction of a ferromagnetic defect creates monopole injection sites at nucleation fields below the critical lattice switching field.
• High-energy monopoles are localized at the defect site and can be controllably propagated through the lattice.
• Defect programming allows precise control over the pathways of inverted macrospins within the ASI array.

Conclusions:

• Tailoring ASI lattice order with ferromagnetic defects provides a method for controllable monopole manipulation.
• This defect-based control of magnetic charges is a crucial step towards developing functional nanomagnonic devices, such as reconfigurable waveguides.