Large spin pumping from epitaxial Y3Fe5O12thin films to Pt and W layers

Abstract

There are two common methods in generating magnetic resonance in FMs for spin pumping, cavity FMR and microstrip waveguides [3,7,8,12,19]. FMR cavities produce modest-strength, uniform rf fields over a relatively large space (cm-scale); while microstrip waveguides produce rf fields typically in micron to sub-mm scale, and when made very close to the FMs, can generate fairly large h rf [12,19]. Since the magnitude of rf field determines the excitation strength for spin pumping and only a few reports on microstrip spin pumping presented values of h rf [12,19], in this letter, we mainly compare our results with previous reports of spin pumping using cavity FMR. respectively, which reach the resolution limit of conventional high-resolution XRD systems, demonstrating excellent crystalline quality. In this letter, we focus on two 20-nm YIG films (YIG-1 and YIG-2) for FMR and spin pumping measurements.Room-temperature FMR measurements of the YIG films are carried out in a cavity at a microwave frequency f = 9.65 GHz and power P rf = 0.2 mW. Figure 3e shows the angular dependence of V ISHE for Pt/YIG-1 and W/YIG-2 normalized by the maximum magnitude of V ISHE at θ H = 90°.The clear sinusoidal shape is characteristic of ISHE since [15]thus confirming that the observed ISHE voltage arises from FMR spin pumping. The spin pumping signals we observed in insulating YIG cannot be explained by artifacts due to thermoelectric or magnetoelectric effects, such as anisotropic magnetoresistance (AMR) or anomalous Hall effect (AHE) [13,16,32,34,35].While a spin current is generated by transfer of angular momentum from YIG to metal, simultaneously, the coupling between YIG and metal exerts an additional damping to the magnetization precession in YIG, resulting in increased linewidths [10,12], as shown in Fig. 5 4 for the three samples before (∆H 0 ) and after (∆H 1 ) the deposition of where G r , γ, and B are the real part of spin mixing conductance, the gyromagnetic ratio, factor and Bohr magnetron, respectively. Using Eq. (2), we obtain = 4.56× 10 14 and 2.30× 10 14 Ω -1 m -2 for Pt/YIG-2 and W/YIG-2, respectively, which agree with the theoretical calculations [36] and are among the highest of reported experimental values [3,5,8,9].Previously, spin pumping of Pt/YIG excited by similar cavity FMR gave ISHE voltages in the µV range [1,9,11,16]. The large spin pumping signals and high spin mixing conductance observed in our YIG films may be attributed to two possible reasons. First, the small thickness (20 nm) of our films compared to LPE films (100 nm or larger) may play an important role, as suggested by a recent report [7] that a 200-nm YIG film shows much higher spin pumping efficiency than 1-µm and 3-µm films excited by a microstrip waveguide. [7,12]. Further investigation of spin pumping in these thin YIG films using microstrip waveguides will access larger dynamic range of spin pumping. In addition, the mV-level ISHE voltages reported here using a moderate h rf will allow miniaturization of spin pumping structures while m...

Systematic variation of spin-orbit coupling withd-orbital filling: Large inverse spin Hall effect in3dtransition metals

“…2(h)] similar to the behavior reported previously [24]. The ISHE-induced charge current I c = V ISHE /R is proportional to the spin current pumped into Cr [7,15]. Figure 2(i) plots the t Cr dependence of V ISHE /Rw, from which we obtain SD = 13.3 ± 2.1 nm by fitting to ISHE SD tanh C SD [25].…”

“…The 2.5-mV ISHE signal measured in YIG/Cr(10 nm) is exceptionally large and comparable to the values detected in 5d metals Ta, W, and Pt on our YIG films [7,15]. This suggests unexpectedly large θ SH and surprisingly strong SOC in Cr.…”

“…SHE depends on the SOC and θ SH is a measure of the strength of SOC. Because of the generally accepted Z 4 dependence of SOC, measurement of θ SH has been focused on heavy elements by SHE [8] or inverse spin Hall effect (ISHE) [9][10][11][12][13][14][15], while 3d metals have rarely been studied [16,17].…”

“…We deposit epitaxial YIG films on (111)-oriented Gd 3 Ga 5 O 12 (GGG) substrates [7,15,22]. A 2θ-ω x-ray diffraction (XRD) scan of a 25-nm YIG film shown in Fig.…”

“…We report a systematic study of the ISHE in a series of 3d transition metals using FMR spin pumping from Y 3 Fe 5 O 12 (YIG) epitaxial films into Ti, V, Cr, Mn, Fe 50 Mn 50 (FeMn), Fe 20 Ni 80 (Py), Ni, and Cu. The large ISHE signals in our YIG-based structures [7,15,[18][19][20][21] provides unprecedented sensitivity for characterizing the ISHE in 3d metals which are expected to have weak SOC. Surprisingly, we detect an ISHE voltage (V ISHE ) exceeding 5 mV in a YIG/Cr(5 nm) bilayer, which is among the highest V ISHE we observed in any materials [7,15].…”