Patterned growth of crystalline Y3Fe5O12 nanostructures with engineered magnetic shape anisotropy

Abstract

We demonstrate patterned growth of epitaxial yttrium iron garnet (YIG) thin films using lithographically defined templates on gadolinium gallium garnet (GGG) substrates. The fabricated YIG nanostructures yield the desired crystallographic orientation, excellent surface morphology, and narrow ferromagnetic resonance (FMR) linewidth (~ 4 Oe). Shape-induced magnetic anisotropy is clearly observed in a patterned array of nanobars engineered to exhibit the larger coercivity (40 Oe) compared with that of continuous films. Both hysteresis loop and angle-dependent FMR spectra measurements indicate that the easy axis aligns along the longitudinal direction of the nanobars, with an effective anisotropy field of 195 Oe. Our work overcomes difficulties in patterning YIG thin films and provides an effective means to control their magnetic properties and magnetic bias conditions. Nanostructured ferromagnetic thin films have been considered as a promising platform in both longstanding fundamental studies of magnetic excitations and technological improvement of spintronic devices. 1 -3 A large variety of magnetic nanostructures, such as nanoparticles, nanowires, and nanodots, have been successfully fabricated and widely studied for ferromagnetic metals such as permalloy and organic-based ferrites, 4-9 demonstrating the great potential of the

Cavity optomagnonics with magnetic textures: Coupling a magnetic vortex to light

“…[6][7][8], where the underlying magnetic ground state is uniform). This is a relevant case to study since: (i) YIG disks at the microscale have been experimentally realized and the arXiv:1806.06727v2 [cond-mat.mes-hall] 8 Dec 2018 2 presence of magnetic vortices demonstrated [31][32][33] (ii) a disk supports optical WGMs while reducing the magnetic volume with respect to a sphere, which could lead to larger optomagnonic couplings, and (iii) the spin excitations in the presence of the vortex are qualitatively different from those on top of a homogeneous magnetization.We combine analytical methods with micromagnetic and finite-element simulations to derive the spatial dependence and the strength of the optomagnonic coupling. We study two qualitatively different regimes that can be accessed by nanostructure-patterning: a very thin micromagnetic disk embedded in an optical cavity, and a thicker microdisk that also serves as the optical cavity ( Fig.…”

Low-damping ferromagnetic resonance in electron-beam patterned, high-Q vanadium tetracyanoethylene magnon cavities

“…When patterned, the damping increases to α ≈ 4 × 10 −4 to 8.74 × 10 −4 for ion-milled films, 10,11 and α ≈ 2.9 × 10 −4 to 5 × 10 −4 for liftoff-based films. [12][13][14] Furthermore, post-growth annealing steps at temperatures as high as 850 • C are generally required to attain even these degraded damping values, and the lowest damping values are only achieved for films deposited on the lattice-matching substrate gadolinium gallium garnet (Gd 3 Ga 5 O 12 , GGG), both of which provide strict limits on direct integration with functional devices. [15][16][17] Vanadium tetracyanoethylene (V [TCNE] x , x ≈ 2), on the other hand, is a lowloss (sub-Gauss linewidth at 9.83 GHz), room-temperature (T c = 600 K) ferrimagnet that can be deposited optimally at 50 • C and 30 mmHg without the need for lattice matching.…”

“…The thinfilm damping result of (3.98 ± 0.22) × 10 −5 places V[TCNE] x films comfortably alongside YIG films as the lowest magnetic damping material currently available, and the retention of that ultra-low damping after patterning is considerably better than the reported values for patterned YIG structures. [10][11][12][13][14] In addition to low-damping, the high-frequency measurements of the thin film and 25 µm disks have Quality (Q) factors, f ∆ f , of over 3,700, competitive with Q factors for YIG thin films. 48 Retaining ultra-low damping and high Q in patterned V[TCNE] x for features as small as 25 µm and as large as millimeters, both relevant length scales for many magnonic cavity applications, 3,14,[49][50][51][52] combined with the flexibility to deposit on most inorganic substrates, positions V[TCNE] x to complement YIG in magnonic and magnetoelectric devices where integration of GGG or high-temperature annealing steps is limiting, such as for small form factors and on-chip integration.…”

Ultra-low damping in lift-off structured yttrium iron garnet thin films

“…However, the fabrication of high-quality thin YIG films requires deposition temperatures over 500C 6,[9][10][11][12][13][14][15][16][17][18] leading to top-down lithographical approach that is ion-beam etching of a previously deposited plain film whereas patterned resist layer serves as a mask.Consequently, this method introduces crystallographic defects, imperfections to surface structure and, in the case of YIG films, causes significant increase of the damping parameter. [19][20][21] Moreover, it does not ensure well-defined structure edges for insulators, which play a crucial role in devices utilizing…”