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

Abstract

The field of magnon spintronics is experiencing an increasing interest in the development of solutions for spin-wave-based data transport and processing technologies that are complementary or alternative to modern CMOS architectures. Nanometer-thin yttrium iron garnet (YIG) films have been the gold standard for insulator-based spintronics to date, but a potential process technology that can deliver perfect, homogeneous large-diameter films is still lacking. We report that liquid phase epitaxy (LPE) enables the deposition of nanometer-thin YIG films with low ferromagnetic resonance losses and consistently high magnetic quality down to a thickness of 20 nm. The obtained epitaxial films are characterized by an ideal stoichiometry and perfect film lattices, which show neither significant compositional strain nor geometric mosaicity, but sharp interfaces. Their magneto-static and dynamic behavior is similar to that of single crystalline bulk YIG. We found, that the Gilbert damping coefficient α is independent of the film thickness and close to 1 × 10 -4 , and that together with an inhomogeneous peak-to-peak linewidth broadening of ∆H 0|| = 0.4 G, these values are among the lowest ever reported for YIG films with a thickness smaller than 40 nm. These results suggest, that nanometer-thin LPE films can be used to fabricate nano-and micro-scaled circuits with the required quality for magnonic devices. The LPE technique is easily scalable to YIG sample diameters of several inches.

A nonlinear magnonic nano-ring resonator

“…The static magnetization of a straight waveguide is uniform and is along the waveguide, which is caused by a strong shape anisotropy and by the small cross-section. We consider Yttrium-Iron-Garnet (YIG) as the material of both the waveguide and the ring: it is chosen for its low damping, allowing for long-range spin-wave propagation 36 . The used material parameters of YIG are described in "Methods.…”

“…1a. The parameters of the nanometer-thick YIG are obtained from the experiment as following 36 : saturation magnetization M s = 1.4 × 10 5 A m −1 , exchange constant A = 3.5 pJ m −1 , and Gilbert damping for most of the structure α = 2 × 10 −4 , except for the ring structure. The Gilbert damping in the ring structure is increased to 2 × 10 −3 to meet the critical coupling condition and the damping at the ends of the simulated structure is set to exponentially increase to 0.2, to prevent spin-wave reflection.…”

Inverse-design magnonic devices

“…1. It is designed based on a 100-nm-thick Yttrium Iron Garnet (YIG) film 33 and consists of one input waveguide, two output waveguides with the same width of 300 nm, and a design region of 1 × 1 μm 2 between them. The design region has been divided into 10 × 10 elements, each with a size of 100 × 100 nm 2 in which the magnetic material (YIG) is allowed to be entirely removed.…”

“…The micromagnetic simulations were performed by the GPU-accelerated simulation package Mumax 3 , including both exchange and dipolar interactions, to calculate the space-and time-dependent magnetization dynamics in the investigated structures 44 . The parameters of a nanometer thick YIG film were used: 33 saturation magnetization M s = 1.4 × 10 5 A/m, exchange constant A = 3.5 pJ/m, and Gilbert damping α = 2 × 10 −4 . In our simulations, the Gilbert damping at the end of the device was set to exponentially increase to 0.5 to avoid spin-wave reflection.…”

Латеральный Спин-Волновой Транспорт В Системе Неидентичных Магнонно-Кристаллических Микроволноводов

“…При таком подходе удается реализовать целый ряд функциональных блоков обработки сигнала на принципах магноники [3,4]. Малая константа затухания СВ в пленках железоиттриевого граната (YIG) толщинами от единиц микрон и вплоть до 20 nm, выращенных методами жидко-фазной эпитаксии [5] либо техникой импульсного лазерного осаждения [6,7] позволяет существенно минимизировать потери при распространении сигнала, закодированного в виде амплитуды и фазы СВ. Диэлектрические свойства YIG позволяют существенно уменьшить омические потери по сравнению с металлическими ферромагнитными пленками.…”