Bias-free spin-wave propagation in a micrometer-thick ferrimagnetic film with perpendicular magnetic anisotropy

Abstract

The isotropic transmission of magnetostatic forward volume spin waves in magnetic films with perpendicular magnetic anisotropy (PMA) is shown to be useful in the implementation of magnon-based micro-conduits. However, to our knowledge, non-magnetic-bias-field spin-wave propagation in a PMA magnetic insulator has not been achieved yet, which constrains the development of magnonic information devices and systems. Herein, we demonstrate a robust, bias-free spin-wave transmission in an 18.5- μm-thick bismuth-doped thulium iron garnet film with PMA. This ferrimagnetic film grown by liquid phase epitaxy exhibits high quality in both its crystal structure and its chemical composition and displays a large PMA field of ∼173 mT. The bias-free and reciprocal propagation of spin waves is demonstrated by all-electrical spectroscopy and provides a group velocity of 4.90 km s−1 and a decay length of 20.5 µm at zero magnetic field. Direct imaging of the remnant state indicates that the bias-free spin waves propagate along the oppositely oriented stripe domains with Bloch-type walls, which are formed by in-plane pre-magnetization. Our work contributes to the construction of isotropic charge-free micro-circuits with high levels of integration and nonvolatility.

Mapping of Spin‐Wave Transport in Thulium Iron Garnet Thin Films Using Diamond Quantum Microscopy

“…We measure spatially resolved maps of the stray magnetic field produced by the microwave excited spin waves and find a SW wavelength (0.8-2 μm), wavevector values in the range of 4-7 rad μm −1 that depends on the amplitude of the applied magnetic field and fits well with the dispersion curve of Damon-Eshbach surface spin waves. The spin waves last for distances up to 80 μm with a decay length l d ≈50 ± 5 μm, much larger than the values found in earlier studies, [20,21] opening new applications using TmIG in magnonic spintronics [1] and quantum magnonics. [43,44] By engineering the microwave striplines we observe a spin-wave interference between two single-mode SW modes excited by the microwave injected into the central and edge sides of the Au stripline.…”

“…[42] In this work, we use NV magnetometry in combination with SW electrical transmission spectroscopy to study the properties (amplitude, group velocity, wavelength, and decay length) of microwave-excited spin waves in 34 nm thick TmIG films grown on GGG substrates. We measure spatially resolved maps of the stray magnetic field produced by the microwave excited spin waves as a function of the amplitude of the applied magnetic field and find a SW wavelength of 0.8-2 μm, SW decay in ≈50 μm, much longer than earlier studies, [20,21] opening new opportunities of using TmIG in magnonic spintronics [1] and quantum magnonics. [43,44] 2.…”

“…The IP and OOP FMR resonance frequencies are determined from the derivative of real S 11 versus H app curves in Figure S3 (see Section S3 Supporting Information). The solid lines in Figure 1dare fits based on the equations of IP and OOP measurements respectively: [18,20,21]…”

“…For SW transmission spectroscopy, we employ an electrical detection method of spin waves using a vector network analyzer (VNA, Keysight model P5004A). [20,21,47] Ground-signal-ground (GSG) type antennas were fabricated on top of the TmIG film. Refer to Figure 2a, Figure S2a, and Section S2 (Supporting Information) for the nanofabrication details.…”

“…[16] TmIG has been successfully grown as a thin film with thicknesses in the range of a few nanometers [17,18] and its magnetic damping constant was determined to be ≈10 −2 through frequency-dependent ferromagnetic resonance (FMR) measurements. [19] Recent spin-wave (SW) electrical transmission studies on undoped [20] and bi-doped [21] TmIG films reported magnetostatic forward volume spin wave modes with a SW group velocity in the range of 0.15-4.9 km s −1 , and a SW decay length in the range of 3.2-20.5 μm respectively. While these results are promising for using TmIG in magnonic spintronics, [1] there is no direct spatial measurement reported yet of its SW transport properties at the submicron scale.…”