Pseudomorphic Yttrium Iron Garnet Thin Films With Low Damping and Inhomogeneous Linewidth Broadening

Abstract

We report measurements of the frequency and temperature dependence of ferro-magnetic resonance (FMR) for a 15-nm-thick yttrium iron garnet (YIG) film grown by off-axis sputtering. Although the FMR linewidth is narrow at room temperature (corresponding to a damping coefficient α = (9.0 ± 0.2) ×10 −4), comparable to previous results for high-quality YIG films of similar thickness, the linewidth increases strongly at low temperatures, by a factor of almost 30. This increase cannot be explained as due to two-magnon scattering from defects at the sample interfaces. We argue that the increased low-temperature linewidth is due to impurity relaxation mechanisms that have been investigated previously in bulk YIG samples. We suggest that the low-temperature linewidth is a useful figure of merit to guide the optimization of thin-film growth protocols because it is a particularly sensitive indicator of impurities.

Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy

“…However, the observed stress values are almost an order of magnitude smaller than, e.g., for as-deposited YIG PLD films on GGG (111) under compressive strain (see, e.g., Refs. [17,23,35,36]). Only by a complex procedure, applying mid-temperature deposition, cooling, and post-annealing treatment, authors of Ref.…”

“…There are several different techniques to grow YIG on different substrates. (i) Pulsed laser deposition (PLD) is an excellent technique for fabricating small samples of nanometer-thin YIG films with narrow ferromagnetic resonance (FMR) linewidths [17,19,21,22,28,[34][35][36] whereas its up-scaling to larger sample dimensions of several inches is challenging. (ii) Magnetron sputtered YIG usually yields wider FMR linewidths, and inhomogeneous line broadening is frequently observed [37][38][39][40].…”

“…Refs. [35,36,[52][53][54][55][56][57]), which favors in-plane magnetization. Large perpendicular magnetic anisotropies, on the other hand, can be found for films under tensile strain, e.g.…”

Increased low-temperature damping in yttrium iron garnet thin films

“…1 High-quality thin films of YIG and related garnets with thicknesses on the 10's of nm scale and below can now be grown by pulsed-laser deposition (PLD), [2][3][4][5][6][7][8][9] off-axis sputtering, [10][11][12][13][14] and molecularbeam epitaxy (MBE). 15 Ferromagnetic resonance (FMR) measurements at room temperature for films grown by all of these techniques show that the FMR linewidth increases with decreasing film thickness, and the frequency dependence of the linewidth has a nonlinear functional form for very thin films (less than ≈ 20 nm) with inplane magnetization.…”

Damping Enhancement in Coherent Ferrite–Insulating-Paramagnet Bilayers

“…Low-dissipation spintronic devices become particularly attractive if insulating ferrite thin films with low magnetic damping can serve as sources of magnon spin currents. Such low-damping ferrites include not only epitaxial garnet ferrites (e.g., YIG) [3][4][5][6][7][8][9][10][11] that have been widely used in studies of insulating spintronics [2][3][4][12][13][14][15] , but also coherently strained epitaxial spinel ferrites [16][17][18] with crucial technical advantages over garnets, such as lower thermal budget for crystallization, higher magnon resonance frequencies, and potential to be integrated coherently with other spinels and perovskites with various functionalities [19][20][21][22] .…”