The non-random walk of chiral magnetic charge carriers in artificial spin ice

Abstract

The flow of magnetic charge carriers (dubbed magnetic monopoles) through frustrated spin ice lattices, governed simply by Coulombic forces, represents a new direction in electromagnetism. Artificial spin ice nanoarrays realise this effect at room temperature, where the magnetic charge is carried by domain walls. Control of domain wall path is one important element of utilizing this new medium. By imaging the transit of domain walls across different connected 2D honeycomb structures we contribute an important aspect which will enable that control to be realized. Although apparently equivalent paths are presented to a domain wall as it approaches a Y-shaped vertex from a bar parallel to the field, we observe a stark non-random path distribution, which we attribute to the chirality of the magnetic charges. These observations are supported by detailed statistical modelling and micromagnetic simulations. The identification of chiral control to magnetic charge path selectivity invites analogy with spintronics.

Magnetization reversal in kagome artificial spin ice studied by first-order reversal curves

“…The magnetic DWs propagate through an interconnection and trigger spins in a neighboring bar to flip, which leads to chains of magnetization reversal. Such chains of overturned magnetic moment are called "Dirac strings", along which the spin ice rule is maintained except for the two ends [7][8][9]. The magnetization reversal in interconnected Kagome artificial spin ice also has a strong angular dependence [20].…”

“…Although artificial spin ice was designed originally to study thermodynamics of isolated nano-bars, recent works have also focused on the field-driven dynamics in interconnected spin ice structures [7][8][9]. In the spin ice structures, the magnetization reversal is usually controlled by the ice rule that governs the number of magnetizations pointing into and out of each vertex to minimize the local magnetostatic energy [8,13]. The magnetization reversal process in the spin ice structures has been systematically studied by real-space imaging techniques [7][8][9][15][16][17][18], magnetic hysteresis loop measurements using the magneto-optic Kerr effect [19 , 20 ] , and magnetoresistance (MR) measurements [16,[21][22][23].…”

“…The artificial structures provide insight into fundamental understanding of magnetic frustration, especially in the degenerate states and charge-ordered states [2,5,[10][11][12][13][14]. Although artificial spin ice was designed originally to study thermodynamics of isolated nano-bars, recent works have also focused on the field-driven dynamics in interconnected spin ice structures [7][8][9]. In the spin ice structures, the magnetization reversal is usually controlled by the ice rule that governs the number of magnetizations pointing into and out of each vertex to minimize the local magnetostatic energy [8,13].…”

“…In the spin ice structures, the magnetization reversal is usually controlled by the ice rule that governs the number of magnetizations pointing into and out of each vertex to minimize the local magnetostatic energy [8,13]. The magnetization reversal process in the spin ice structures has been systematically studied by real-space imaging techniques [7][8][9][15][16][17][18], magnetic hysteresis loop measurements using the magneto-optic Kerr effect [19 , 20 ] , and magnetoresistance (MR) measurements [16,[21][22][23]. The correlation between the magnetization switching and the associated MR change during the reversal process was carefully investigated recently [23].…”

Fast generation of domain walls with defined chirality in nanowires

“…For example, in artificial spin ice systems, the path of a vortex domain wall through the Y-shaped junctions depends on its sense of chirality. 11,12 Here, we demonstrate the controlled generation of domain walls with defined chirality on a nanosecond timescale in permalloy ðNi 80 Fe 20 Þ nanowires with a tilted stripline. The samples are prepared by two electron-beam lithography steps with positive PMMA resists and lift-off technique.…”