Spin-Wave Dynamics in an Artificial Kagome Spin Ice

Abstract

Artificial spin ice (ASI) structures have significant technological potential as reconfigurable metamaterials and magnetic storage media. We investigate the field/frequency-dependent magnetic dynamics of a kagome ASI made of 25-nm-thick permalloy nanomagnet elements, combining magnetoresistance (MR) and microscale ferromagnetic resonance (FMR) techniques. Our FMR spectra show a broadband absorption spectrum from 0.2 GHz to 3 GHz at H below 0.3 kOe, where the magnetic configuration of the kagome ASI is in the multidomain state, because the external magnetic field is below the obtained coercive field H c ∼ 0.3 kOe, based on both the low-field range MR loops and simulations, suggesting that the low-field magnetization dynamics of kagome ASI is dominated by a multimode resonance regime. However, the FMR spectra exhibit five distinctive resonance modes at the high-field quasi-uniform magnetization state. Furthermore, our micromagnetic simulations provide additional spatial resolution of these resonance modes, identifying the presence of two high-frequency primary modes, localized in the horizontal and vertical bars of the ASI, respectively; three other low-frequency modes are mutually exclusive and separately pinned at the corners of the kagome ASI by an edge-induced dipolar field. Our results suggest that an ASI structural design can be adopted as an efficient approach for the development of low-power filters and magnonic devices.

Thickness-dependent magnetic properties in Pt/[Co/Ni] n multilayers with perpendicular magnetic anisotropy

“…4(a)]. [16,30] The differential absorption signal is measured by sweeping the magnetic field with a fixed microwave frequency. The representative FMR spectrum of Pt( 5)/[Co(0.2)/Ni(0.3)] 5 /Pt(1) obtained at 9 GHz is shown in the inset of Fig.…”

“…The magnetic multilayers, e.g., [Co/Pd], [Co/Pt], and [Co/Ni], provide an opportunity to tune their magnetic properties by changing the thickness ratio controllably and the number of bilayer repeats thanks to the interface-induced PMA due to interfacial spin-orbit coupling and interfacial strain relevant magnetoelastic effects. [12][13][14][15][16][17] Among these PMA multilay-ers, the PMA [Co/Ni] multilayer also exhibits low damping constant, [14] which gets much attention, especially for the fields of current-driven auto-oscillation of magnetization and excitation and manipulation of spin-waves. [18,19] Furthermore, the PMA [Co/Ni] multilayer is also useful for spin-orbit torque devices.…”