Spin-Hall magnetoresistance in platinum on yttrium iron garnet Vlietstra, N.; Shan, J.; Castel, V.; van Wees, B. J.; Ben Youssef, J. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. The occurrence of spin-Hall magnetoresistance (SMR) in platinum (Pt) on top of yttrium iron garnet (YIG) has been investigated, for both in-plane and out-of-plane applied magnetic fields and for different Pt thicknesses [3, 4, 8, and 35 nm]. Our experiments show that the SMR signal directly depends on the in-plane and out-of-plane magnetization directions of the YIG. This confirms the theoretical description, where the SMR occurs due to the interplay of the spin-orbit interaction in the Pt and the spin-mixing conductance at the YIG/Pt interface. Additionally, the sensitivity of the SMR and spin pumping signals on the YIG/Pt interface conditions is shown by comparing two different deposition techniques (e-beam evaporation and dc sputtering).

We investigate the spin Hall magnetoresistance in thin film bilayer heterostructures of the heavy metal Pt and the antiferromagnetic insulator NiO. While rotating an external magnetic field in the easy plane of NiO, we record the longitudinal and the transverse resistivity of the Pt layer and observe an amplitude modulation consistent with the spin Hall magnetoresistance. In comparison to Pt on collinear ferrimagnets, the modulation is phase shifted by 90 • and its amplitude strongly increases with the magnitude of the magnetic field. We explain the observed magnetic field-dependence of the spin Hall magnetoresistance in a comprehensive model taking into account magnetic field induced modifications of the domain structure in antiferromagnets. With this generic model we are further able to estimate the strength of the magnetoelastic coupling in antiferromagnets. Our detailed study shows that the spin Hall magnetoresistance is a versatile tool to investigate the magnetic spin structure as well as magnetoelastic effects, even in antiferromagnetic multi-domain materials. J c J s σ large ρ J c J s σ FMI HM FMI HM (a) (b) j t n J s stt J s back J c J c J s σ AFI HM AFI HM J s stt J s back FMI/HM bilayer AFI/HM bilayer m m * stephan.gepraegs@wmi.badw.de

We studied the nonlocal transport behavior of both electrically and thermally excited magnons in yttrium iron garnet (YIG) as a function of its thickness. For electrically injected magnons, the nonlocal signals decrease monotonically as the YIG thickness increases. For the nonlocal behavior of the thermally generated magnons, or the nonlocal spin Seebeck effect (SSE), we observed a sign reversal which occurs at a certain heater-detector distance, and it is influenced by both the opacity of the YIG/heater interface and the YIG thickness. Our nonlocal SSE results can be qualitatively explained by the bulk-driven SSE mechanism together with the magnon diffusion model. Using a two-dimensional finite element model (2D-FEM), we estimated the bulk spin Seebeck coefficient of YIG at room temperature. The quantitative disagreement between the experimental and modeled results indicates more complex processes going on in addition to magnon diffusion and relaxation, especially close to the contacts.

The effective field torque of an yttrium-iron-garnet (YIG) film on the spin accumulation in an attached platinum (Pt) film is measured by the spin-Hall magnetoresistance (SMR). As a result, the magnetization direction of a ferromagnetic insulating layer can be measured electrically. Experimental transverse and longitudinal resistances are well described by the theoretical model of SMR in terms of the direct and inverse spin-Hall effect, for different Pt thicknesses [3, 4, 8, and 35 nm]. Adopting a spin-Hall angle of Pt h SH ¼ 0:08, we obtain the spin diffusion length of Pt (k ¼ 1:1 6 0:3 nm) as well as the real (G r ¼ ð7 6 3Þ Â 10 14 X À1 m À2 ) and imaginary part (G i ¼ ð5 6 3Þ Â 10 13 X À1 m À2 ) of the spin-mixing conductance and their ratio (G r =G i ¼ 16 6 4). In spintronics, interfaces between magnets and normal metals are important for the creation and detection of spin currents, which is governed by the difference of the electric conductance for spin up and spin down electrons.1-3 Another important interaction between the electron spins in the magnetic layer and those in the normal metal, that are polarized perpendicular to the magnetization direction, is governed by the spin-mixing conductance G "# , 4 which is composed of a real part and an imaginary part (G "# ¼ G r þ iG i ). G r is associated with the "in-plane" or "Slonczewski" torque along m Âl Âm, 5-7 wherem is the direction of the magnetization of the ferromagnetic layer andl is the polarization of the spin accumulation at the interface. G i describes an exchange magnetic field that causes precession of the spin accumulation aroundm. This "effective-field" torque associated with G i points towardsl Âm.While several experiments succeeded in measuring G r , 3,4,7-10 G i is difficult to determine experimentally, mainly because it is usually an order of magnitude smaller than G r . 4The recently discovered spin-Hall magnetoresistance (SMR) 11-14 offers the unique possibility to measure G i for an interface of a normal metal and a magnetic insulator by exposing it to out-of-plane magnetic fields. Althammer et al.15 carried out a quantitative study of the SMR of Yttrium Iron Garnet (YIG)/Platinum (Pt) bilayers. They obtained an estimate of G i ¼ 1:1 Â 10 13 X À1 m À2 by extrapolating the high field Hall resistances to zero magnetic field. 16In this paper, we report experiments in which the contribution of G r and G i can be controlled by changing the magnetization direction of the YIG layer by an external magnetic field. Thereby either G r or G i can be made to dominate the SMR. By fitting the experimental data by the theoretical model for the SMR, 11 the magnitude of G r , G i , and the spin diffusion length k in Pt are determined.For SMR measurements, Pt Hall bars with thicknesses of 3, 4, 8, and 35 nm were deposited on YIG by dc sputtering.12 Simultaneously, a reference sample was fabricated on a Si/SiO 2 substrate. The length and width of the Hall bars are 800 lm and 100 lm, respectively. The YIG has a thickness of 200 nm and is grown by liquid ...

We show the first experimental observation of the platinum (Pt) thickness dependence in a hybrid YIG/Pt system of the inverse spin-Hall effect from spin pumping, over a large frequency range and for different rf powers. From the measurement of the dc voltage (∆V) at the resonant condition and the resistance (R) of the Pt layer, a strong enhancement of the ratio ∆V/R has been observed, which is not in agreement with previous studies on the NiFe/Pt system. The origin of this behaviour is still unclear and cannot be explained by the spin transport model that we have used.