Tunable magnetization dynamics in artificial spin ice via shape anisotropy modification

Abstract

Ferromagnetic resonance (FMR) is performed on kagome artificial spin ice (ASI) formed of disconnected Ni 80 Fe 20 nanowires. Here we break the threefold angular symmetry of the kagome lattice by altering the coercive field of each sublattice via shape anisotropy modification. This allows for distinct high-frequency responses when a magnetic field is aligned along each sublattice and additionally enables simultaneous spin-wave resonances to be excited in all nanowire sublattices, unachievable in conventional kagome ASI. The different coercive field of each sublattice allows selective magnetic switching via global field, unlocking novel microstates inaccessible in homogeneous-nanowire ASI. The distinct spin-wave spectra of these states are detected experimentally via FMR and linked to underlying microstates using micromagnetic simulation.

Magnetic Tunability of Permalloy Artificial Spin Ice Structures

“…As a result, most of the research attempts highlight the 2331-7019/20/13(1)/014034 (10) 014034-1 © 2020 American Physical Society manipulation of the degeneracy of magnetic ground state and observation of magnetic monopoles with the analysis of spin mapping and correlation of spins at different vertex using magnetic force microscopy (MFM) [22,27], x-ray magnetic circular dichroism (XMCD) photoemission electron microscopy (PEEM) [28][29][30], and Lorentz microscopy [31]. Apart from the static magnetic properties of ASI, tunability in magnetization dynamics by breaking the angular symmetry of the structure [32] and geometry-dependent existence of magnon modes [33,34] have been reported. Recently, the tenability of the ice rules, ground state degeneracy has also been reported for aperiodic structures [35], pinwheel structures [36], and colloidal systems [37].…”

Current-controlled nanomagnetic writing for reconfigurable magnonic crystals

“…Figure 4e shows the resultant spin-wave spectra, with two distinct modes present for each microstate; a nanoisland-edge localized 1-3 GHz mode (f edge of 2.43, 1.78 and 2.74 GHz for FM, AFM and stripe, respectively), and a nanoisland-centre localized 5-8 GHz mode, with spatial mode profiles displayed next to each peak. The cause of distinct modes in each microstate is the differing local field H loc profile from nanoisland stray dipolar fields [58][59][60][61][62][63][64][65] . These are at their strongest at the nanoisland edges and it follows that the edge-localized modes display greater microstate sensitivity.…”

Dynamically Driven Emergence in a Nanomagnetic System

“…In nanoscale magnetic systems, emergent behavior has been observed in artificial spin ice (ASI) systems, where simple dipolar/exchange couplings between neighboring nanomagnets result in a variety of complex and elegant collective phenomena. [ 15–19 ] These emergent behaviors have been proposed for use in novel computational paradigms such as reservoir computing [ 16 ] or Hopfield networks for pattern recognition. [ 17 ] Magnetic fields have been applied to ASIs to simulate the demagnetization from thermal annealing [ 20 ] and to study high‐speed dynamics, [ 15,19 ] but there are few reports of continuous field‐driven dynamic complexity in ASIs.…”

“…[ 15–19 ] These emergent behaviors have been proposed for use in novel computational paradigms such as reservoir computing [ 16 ] or Hopfield networks for pattern recognition. [ 17 ] Magnetic fields have been applied to ASIs to simulate the demagnetization from thermal annealing [ 20 ] and to study high‐speed dynamics, [ 15,19 ] but there are few reports of continuous field‐driven dynamic complexity in ASIs. [ 16 ] To realize the potential of emergent behavior in nanomagnetic systems for device applications, systems must be found in which it is possible to drive these behaviors directly with applied magnetic fields or spin torques.…”