Platinum thickness dependence of the inverse spin-Hall voltage from spin pumping in a hybrid YIG/Pt system (original) (raw)
Related papers
Applied Physics Letters, 2012
Negative magnetoresistance and anomalous Hall effect in GeMnTe-SnMnTe spin-glass-like system J. Appl. Phys. 113, 063702 (2013) Optimization of Hall bar response to localized magnetic and electric fields J. Appl. Phys. 113, 064504 Search for long-range ferromagnetism: Charge-spin co-doped Ba1−x−yLax+yTi1−xMxO3 (M = Cr, Fe, and Co) J. Appl. Phys. 113, 063902 (2013) Crystalline anisotropic magnetoresistance in quaternary ferromagnetic semiconductor (Ga,Mn)(As,Sb) Appl. Phys. Lett. 102, 052407 (2013) Additional information on Appl. Phys. Lett.
Frequency and power dependence of spin-current emission by spin pumping in a thin-film YIG/Pt system
Physical Review B, 2012
This paper presents the frequency dependence of the spin-current emission by spin pumping in a hybrid ferrimagnetic insulator/normal metal system. The system is based on a ferrimagnetic insulating thin film of yttrium iron garnet (YIG, 200 nm) grown by liquid-phase epitaxy coupled with a normal metal with a strong spin-orbit coupling (Pt, 15 nm). The YIG layer presents an isotropic behavior of the magnetization in the plane, a small linewidth, and a roughness lower than 0.4 nm. Here we discuss how the voltage signal from the spin-current detector depends on the frequency (0.6-7 GHz), the microwave power, P in (1-70 mW), and the in-plane static magnetic field. A strong enhancement of the spin-current emission is observed at low frequencies, showing the appearance of nonlinear phenomena.
We report the frequency dependence of the spin current emission (spin pumping) in a hybrid ferrimagnetic insulator/normal metal system as a function of the insulating layer thickness. The system is based on an yttrium iron garnet (YIG) film [0.2, 1, and 3 μm] grown by liquid-phase epitaxy coupled with a spin current detector of platinum[6 nm]. A strong YIG thickness dependence of the efficiency of the spin pumping has been observed. The highest conversion factor V /P abs has been demonstrated for the thinner YIG (1.79 and 0.55 mV/mW at 2.5 and 10 GHz, respectively), which is of interest for research heading towards YIG-based devices. Furthermore, we demonstrate the threshold frequency dependence of the three-magnon splitting process, which is shown to cease to exist for the thinner YIG of 0.2 μm.
Comparative measurements of inverse spin Hall effects and magnetoresistance in YIG/Pt and YIG/Ta
Physical Review B, 2013
We report on a comparative study of spin Hall related effects and magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements allow to estimate the characteristic transport parameters of both Pt and Ta layers juxtaposed to YIG: the spin mixing conductance G ↑↓ at the YIG|normal metal interface, the spin Hall angle ΘSH, and the spin diffusion length λ sd in the normal metal. The inverse spin Hall voltages generated in Pt and Ta by the pure spin current pumped from YIG excited at resonance confirm the opposite signs of spin Hall angles in these two materials. Moreover, from the dependence of the inverse spin Hall voltage on the Ta thickness, we extract the spin diffusion length in Ta, found to be λ Ta sd = 1.8 ± 0.7 nm. Both the YIG|Pt and YIG|Ta systems display a similar variation of resistance upon magnetic field orientation, which can be explained in the recently developed framework of spin Hall magnetoresistance.
Physical Review B, 2015
The dependence of the spin-pumping effect on the yttrium iron garnet (Y3Fe5O12, YIG) thickness detected by the inverse spin Hall effect (ISHE) has been investigated quantitatively. Due to the spinpumping effect driven by the magnetization precession in the ferrimagnetic insulator Y3Fe5O12 film a spin-polarized electron current is injected into the Pt layer. This spin current is transformed into electrical charge current by means of the ISHE. An increase of the ISHE-voltage with increasing film thickness is observed and compared to the theoretically expected behavior. The effective damping parameter of the YIG/Pt samples is found to be enhanced with decreasing Y3Fe5O12 film thickness. The investigated samples exhibit a spin mixing conductance of g ↑↓ eff = (3.87±0.21)×10 18 m −2 and a spin Hall angle between θISHE = 0.013 ± 0.001 and 0.045 ± 0.004 depending on the used spindiffusion length. Furthermore, the influence of nonlinear effects on the generated voltage and on the Gilbert damping parameter at high excitation powers are revealed. It is shown that for small YIG film thicknesses a broadening of the linewidth due to nonlinear effects at high excitation powers is suppressed because of a lack of nonlinear multi-magnon scattering channels. We have found that the variation of the spin-pumping efficiency for thick YIG samples exhibiting pronounced nonlinear effects is much smaller than the nonlinear enhancement of the damping.
Applied Physics Letters, 2014
We study the temperature dependence of the spin Hall magnetoresistance (SMR) in yttrium iron garnet/platinum hybrid structures via magnetization orientation dependent magnetoresistance measurements. Our experiments show a decrease of the SMR magnitude with decreasing temperature. Using the sensitivity of the SMR to the spin transport properties of the normal metal, we interpret our data in terms of a decrease of the spin Hall angle in platinum from 0.11 at room temperature to 0.075 at 10 K, while the spin diffusion length and the spin mixing conductance of the ferrimagnetic insulator/normal metal interface remain almost constant.
Physical Review Letters, 2014
It was recently realized that the spin Hall effect (SHE) can be very useful in the area of spintronics, due to its ability to generate pure spin current from charge current, without the use of any magnetic materials or magnetic field. The maximum conversion factor is given by the spin Hall angle SH , which can take rather important values (above 10% in absolute value was reported for β-Ta and β-W). This phenomenon is usually observed in materials with large spin-orbit coupling, either intrinsic (Pt, Ta, W, etc.) or induced by heavy impurities (Cu doped with Bi or Ir). To investigate this property, several groups studied the reciprocal effect, the so-called inverse spin Hall effect (ISHE), converting a pure "pumped" spin current into a charge current (measured by voltage detection in an "open circuit"). We focus here on the 5d Pt material. Values published nowadays for SH in Pt are scattered over one order of magnitude, with a clear correlation between the spin diffusion length ℓ sf and the SH , both quantities being related to the spin-orbit strength or its inverse. We performed measurements of spin pumping in a cavity and measured the resulting ISHE voltage. We propose a model including spin-current discontinuity or spin memory loss at the interfaces that may reconcile all the different observations. In particular, we demonstrate consistent values of spin diffusion length (ℓ sf = 3.4 ± 0.4 nm) and spin Hall angle ( SH = 0.056 ± 0.010) for Pt in different metallic multilayer systems.
Physical Review B, 2013
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).
Enhancement of YIG|Pt spin conductance by local Joule annealing
Applied Physics Letters, 2021
We report that Joule heating can be used to enhance the interfacial spin conductivity between a metal and an oxide. We observe that local annealing of the interface at about 550 K, when injecting large current densities (>1012A/m2) into a pristine 7 nm thick Pt nanostrip evaporated on top of yttrium iron garnet (YIG), can improve the effective spin transmission up to a factor of 3. This result is of particular interest when interfacing ultrathin garnet films to avoid strong chemical etching of the surface. The effect is confirmed by the following methods: spin Hall magnetoresistance, spin pumping, and non-local spin transport. We use it to study the influence of the YIG|Pt coupling on the non-linear spin transport properties. We find that the crossover current from a linear to a non-linear spin transport regime is independent of this coupling.
Journal of Physics D: Applied Physics, 2014
We carried out a concerted effort to determine the absolute sign of the inverse spin Hall effect voltage generated by spin currents injected into a normal metal. We focus on yttrium iron garnet (YIG)|platinum bilayers at room temperature, generating spin currents by microwaves and temperature gradients. We find consistent results for different samples and measurement setups that agree with theory. We suggest a right-hand-rule to define a positive spin Hall angle corresponding to with the voltage expected for the simple case of scattering of free electrons from repulsive Coulomb charges.