We experimentally investigate and quantitatively analyze the spin Hall magnetoresistance effect in ferromagnetic insulator/platinum and ferromagnetic insulator/nonferromagnetic metal/platinum hybrid structures. For the ferromagnetic insulator, we use either yttrium iron garnet, nickel ferrite, or magnetite and for the nonferromagnet, copper or gold. The spin Hall magnetoresistance effect is theoretically ascribed to the combined action of spin Hall and inverse spin Hall effect in the platinum metal top layer. It therefore should characteristically depend upon the orientation of the magnetization in the adjacent ferromagnet and prevail even if an additional, nonferromagnetic metal layer is inserted between Pt and the ferromagnet. Our experimental data corroborate these theoretical conjectures. Using the spin Hall magnetoresistance theory to analyze our data, we extract the spin Hall angle and the spin diffusion length in platinum. For a spin-mixing conductance of 4 × 10 14 −1 m −2 , we obtain a spin Hall angle of 0.11 ± 0.08 and a spin diffusion length of (1.5 ± 0.5) nm for Pt in our thin-film samples.

Surface acoustic waves (SAWs) in the GHz frequency range are exploited for the all-elastic excitation and detection of ferromagnetic resonance (FMR) in a ferromagnetic-ferroelectric (Ni/LiNbO(3)) hybrid device. We measure the SAW magnetotransmission at room temperature as a function of frequency, external magnetic field magnitude, and orientation. Our data are well described by a modified Landau-Lifshitz-Gilbert approach, in which a virtual, strain-induced tickle field drives the magnetization precession. This causes a distinct magnetic field orientation dependence of elastically driven FMR that we observe in both model and experiment.

Proposals for novel spin--orbitronic logic 1 and memory devices 2 are often predicated on assumptions as to how materials with large spin--orbit coupling interact with ferromagnets when in contact. Such interactions give rise to a host of novel phenomena, such as spin--orbit torques 3,4 , chiral spin--structures 5,6 and chiral spin--torques 7,8 . These chiral properties are related to the anti--symmetric exchange, also referred to as the interfacial Dzyaloshinskii--Moriya interaction (DMI) 9,10 . For numerous phenomena, the relative strengths of the symmetric Heisenberg exchange and the DMI is of great importance. Here, we use optical spin--wave spectroscopy (Brillouin light scattering) to directly determine the DMI vector ! D for a series of Ni 80 Fe 20 /Pt samples, and then compare the nearest--neighbor DMI coupling energy with the independently measured Heisenberg exchange integral. We find that the Ni 80 Fe 20 --thickness--dependencies of both the microscopic symmetric--and antisymmetric--exchange are identical, consistent with the notion that the basic mechanisms of the DMI and Heisenberg exchange essentially share the same underlying physics, as was originally proposed by Moriya 11 . While of significant fundamental importance, this result also leads us to a deeper understanding of DMI and how it could be optimized for spin--orbitronic applications.Recent experimental results have demonstrated how the interplay of symmetric (Heisenberg) exchange and anti--symmetric (DMI) exchange together with anisotropy can give rise to a variety of magnetostatic phenomena, such as magnetic skyrmion lattices 12 , spiral spin structures 13 and chiral domain walls 14 . In bilayer materials with a sufficiently thin, perpendicular magnetized ferromagnet (FM) adjacent to a metal with large spin--orbit coupling in the conduction band, a large DMI favors Néel domain walls with a fixed chirality 15 as opposed to Bloch walls. The combination of a chiral domain wall structure and spin--orbit torque can give rise to fast current induced domain wall motion 3 . The direction and the speed are both dependent on the sign and the strength of the DMI and the spin--orbit torque 8,7 . Moreover, theory for a Rashba model predicts that the interfacial spin--orbit torque is proportional to the ratio of symmetric and anti--symmetric exchange 16 . Thus, direct determination of both the DMI and Heisenberg exchange is crucial for the understanding of the underlying physics in such materials systems and a better understanding of the spin--orbit torques.To date, direct measurements of anti--symmetric exchange are limited to exotic measurement techniques that can only be applied to a few highly specialized sample systems. For example, the DMI constant has been measured via synchrotron--based X--ray scattering interferometry for the weak ferromagnet FeBO 3 17 , by spin--polarized electron energy loss spectroscopy for an atomic bilayer of Fe on W(110) 18 and by spin--polarized scanning tunneling microscopy for atomic monolayer Mn on W(110) 5 .Until...

We perform a quantitative, comparative study of the spin pumping, spin Seebeck and spin Hall magnetoresistance effects, all detected via the inverse spin Hall effect in a series of over 20 yttrium iron garnet/Pt samples. Our experimental results fully support present, exclusively spin currentbased, theoretical models using a single set of plausible parameters for spin mixing conductance, spin Hall angle and spin diffusion length. Our findings establish the purely spintronic nature of the aforementioned effects and provide a quantitative description in particular of the spin Seebeck effect.Pure spin currents present a new paradigm in spintronics [1, 2] and spin caloritronics [3]. In particular, spin currents are the origin of spin pumping [4,5], the spin Seebeck effect [6,7] and the spin Hall magnetoresistance (SMR) [8][9][10]. Taken alone, all these effects have been extensively studied, both experimentally [6-9, 11-13] and theoretically [4,[14][15][16][17][18]. From a theoretical point of view, all these effects are governed by the generation of a current of angular momentum via a non-equilibrium process. The flow of this spin current across a ferromagnet/normal metal interface can then be detected. The relevant interface property that determines the spin current transport thereby is the spin mixing conductance. Nevertheless, there has been an ongoing debate regarding the physical origin of the measurement data acquired in spin Seebeck and SMR experiments due to possible contamination with anomalous Nernst effect [19][20][21] or anisotropic magnetoresistance [22,23] caused by static proximity polarization of the normal metal [23]. To settle this issue, a rigorous check of the consistency of the spin-current based physical models across all three effects is needed. If possible contamination effects are absent, according to the spin mixing conductance concept [24], there should exist a generalized Ohm's law between the interfacial spin current and the energy associated with the corresponding non-equilibrium process. This relation should invariably hold for the spin pumping, spin Seebeck and spin Hall magnetoresistance effects, as they are all based on the generation and detection of interfacial, nonequilibrium spin currents. We here put forward heuristic arguments that are strongly supported by experimental evidence for a scaling law that links all aforementioned spin(calori)tronic effects on a fundamental level and allows to trace back their origin to pure spin currents. (c) The spin Hall magnetoresistance is due to the torque exerted on M by an appropriately polarized Js which yields a change in the reflected spin current J r s . The interconversion between Js (J r s ) and the charge currents Jc (J r c ) are due to the (inverse) spin Hall effect in the normal metal.[schematically depicted in Fig. 1(a)], we place YIG / Pt bilayers in a microwave cavity operated at ν = 9.85 GHz to resonantly excite magnetization dynamics. The emission of a spin current density J s across the bilayer interface into the Pt provides...