Detecting single nanomagnet dynamics beyond the diffraction limit in varying magnetostatic environments

Abstract

As areal bit density increases, characterizing individual magnetic bits within dense arrays becomes difficult with diffraction-limited optics. We demonstrate that dynamic magneto-optical detection breaks this diffraction limit if the characteristic behavior of a nanomagnet is sufficiently different from its neighbors’. We use far-field time-resolved Kerr microscopy to resolve the high-frequency magnetization dynamics of a single, small (Ø150 nm) nanomagnet within a low-frequency background from an array of large (Ø500 nm) magnets. We use this technique to observe and quantify the effects of magnetostatic interactions on the single magnet dynamics as the intermagnet spacing is varied.

Controlling nanomagnet magnetization dynamics via magnetoelastic coupling

“…2d), but modified by the shape-dependent demagnetization field and magneto-static interelement interactions. The latter are much smaller than previously reported configurations [8] due to the smaller stray field from the thinner and smaller nanomagnets. The low-field behavior is in excellent agreement with simulations that include only these magnetic contributions (dashed line).…”

“…Studies on single nanomagnets as well as ensemble measurements have revealed the influence of the two-and threedimensional shape [4,5] and the fabrication process [2] of the individual nanomagnets on the spin wave spectrum. It has also been shown that magnetic interactions between densely packed magnets result in deviations from single magnet behavior in terms of resonance frequency shifts [8] and dynamic dephasing (damping) of the ensemble signal [9]. Periodic arrays of non-magnetic materials, on the other hand, were shown to exhibit oscillations in their time-dependent reflectivity due to the generation of elastic waves in these phononic crystals [10,11].…”

“…1a) fabricated using electron beam lithography with electron beam deposition and liftoff on a (100) silicon substrate with a 110-nm thick hafnium oxide antireflection (AR) coating that helps maximize the magneto-optical signal [8,19]. The major and minor diameters of the ellipses were 140 and 80 nm, respectively, as measured by scanning electron microscopy.…”

“…A variety of techniques including ferromagnetic resonance [1], Brillouin light scattering [2], X-ray spectroscopy [3], and the timeresolved magneto-optic Kerr effect (TR-MOKE) [4][5][6][7][8] have been used to access dynamic processes on the pico-and femtosecond time scale. Studies on single nanomagnets as well as ensemble measurements have revealed the influence of the two-and threedimensional shape [4,5] and the fabrication process [2] of the individual nanomagnets on the spin wave spectrum.…”

Asymmetry of spin wave dispersions in a hexagonal magnonic crystal

“…3,5,9,10 Dense arrays of in-plane magnetized nano-disks have been extensively investigated by ferromagnetic resonance, [11][12][13][14][15] Brillouin light scattering (BLS), [16][17][18][19][20][21][22][23] and time resolved magneto-optical measurements. [24][25][26][27][28] However, arrays of disks arranged into a hexagonal mesh have been sparsely studied so far, and the experimental data have been presented for wave vector k ¼ 0 only. 29 This is probably due to the fact that arrays of disks arranged in the hexagonal symmetry are challenging not only from the fabrication and characterization perspective but also from the point of view of their theoretical modeling.…”