![]() Quasi-parallel pumping ( H ∥ h ) is realized when the coaxial short is parallel to the y axis, as shown in Fig. Pure perpendicular pumping ( H ⊥ h ) is achieved when the resonator short is collinear with the z axis. The orientation of the resonator short defines the orientation of microwave field and hence the microwave pumping condition. The threshold microwave field h th m above which parametric excitation can occur is given by 20 h th m = Q L π f p β 1 + β P th, where P th is the threshold microwave power. 19 The loaded quality factors Q L and coupling coefficients β are measured for all resonator modes used in the experiment. The microwave field h is generated by a shorted coaxial resonator. The experimental setup is schematically shown in Fig. The typical linewidth of our YIG films in the absence of Pt 18 is ∼10 Oe 9.65 GHz. The magnetic properties of our YIG/Pt sample were measured to be saturation magnetization 4 π M s = 1650 G, saturation field H sat = 25 Oe, and uniform mode linewidth Δ H = 23 Oe 9.65 GHz. Indium contacts are attached to the Pt layer near the edges of the sample, and the center of the sample is covered with a 200 nm thick SiO 2 layer. 14 The spin sensing layer is a 5 nm thick sputtered Pt film with resistance 660 Ohm. The YIG used in this experiment is a (111)-oriented thin film epitaxially grown on a (111) gadolinium gallium garnet substrate. 13 Also, the extraordinarily strong spin pumping signals detected in our thin YIG films 2,14 make it a very promising candidate for spintronics applications, especially in light of the recent demonstration of electrical control of spinwave damping in YIG. This is smaller than spinwave wavevectors used in many spin transfer torque experiments. ![]() 11,12 However, the highest wavevector range covered in experiments with thin films 11 has yet to exceed k ≳ 4 μ m − 1 and has only been reported for standing wave modes. 3 Spin pumping from spinwaves has been studied previously in thick 4–10 and thin film YIG. An important material for these applications is yttrium iron garnet (YIG), a ferrimagnetic insulator with low magnetic losses, which makes YIG an ideal spinwave conductor. 1,2 However, angular momentum transfer from excitations with much higher wavevectors k is potentially attractive for applications, allowing for further miniaturization and an associated increase of operational frequencies for spintronic devices. Most previous spin pumping experiments address the uniform (i.e., k = 0) mode of ferromagnetic resonance (FMR). Spin pumping from spinwaves allows for angular momentum transfer from high frequency finite wavelength magnetic excitations of a ferromagnet into an adjacent normal metal layer.
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