J. Holanda

Dirac-surface-state-dominated spin to charge current conversion in the topological insulator ( Bi0.22Sb0.78)2Te3 films at room temperature

We report the spin to charge current conversation in an intrinsic topological insulator (TI)

Spin Seebeck effect in the antiferromagnet nickel oxide at room temperature

(Bi_{0.22}Sb_{0.78})_2Te_3

Giant Zeeman shifts in the optical transitions of yttrium iron garnet thin films

film at room temperature. The spin currents are generated in a thin layer of permalloy (Py) by two different processes, spin pumping (SPE) and spin Seebeck effects (SSE). In the first we use microwave-driven ferromagnetic resonance of the Py film to generate a SPE spin current that is injected into the TI

Nonlinear dynamics of three-magnon process driven by ferromagnetic resonance in yttrium iron garnet

(Bi_{0.22}Sb_{0.78})_2Te_3

Efficient spin to charge current conversion in the 2D semiconductor MoS2 by spin pumping from yttrium iron garnet

layer in direct contact with Py. In the second we use the SSE in the longitudinal configuration in Py without contamination by the Nernst effect made possible with a thin NiO layer between the Py and

Spin-flop transition in the easy-plane antiferromagnet nickel oxide

(Bi_{0.22}Sb_{0.78})_2Te_3

Longitudinal spin Seebeck effect in permalloy separated from the anomalous Nernst effect: Theory and experiment

layers. The spin-to-charge current conversion is attributed to the inverse Edelstein effect (IEE) made possible by the spin-momentum locking in the electron Fermi contours due to the Rashba field. The measurements by the two techniques yield very similar values for the IEE parameter, which are larger than the reported values in the previous studies on topological insulators.

Detecting the phonon spin in magnon–phonon conversion experiments

The generation of spin currents by thermal gradients applied to a magnetic film is known as the spin Seebeck effect (SSE). The SSE is usually detected by an electric voltage generated in a metallic layer in contact with the magnetic film produced by the spin to charge current conversion through the inverse spin Hall effect (ISHE). The SSE has been widely studied in bilayers made of the insulating ferrimagnet yttrium iron garnet (YIG) and metals with large spin orbit coupling, such as platinum. Recently, the SSE has been observed in bilayers made of the antiferromagnets MnF2 and Cr2O3 with Pt at low temperatures and high magnetic fields. Here, we report measurements of the SSE at room temperature and low magnetic fields in bilayers made of well textured films of antiferromagnetic NiO with several metals. The detection of the spin current generated by the thermal gradient in the NiO layer is made by means of the ISHE in the nonmagnetic metals Pt and Ta, in the AF metal IrMn, and in the ferromagnetic metal N...

Simultaneous spin pumping and spin Seebeck experiments with thermal control of the magnetic damping in bilayers of yttrium iron garnet and heavy metals: YIG/Pt and YIG/IrMn

We report the observation of giant Zeeman shifts in the optical transitions of high-quality very thin films of yttrium iron garnet (YIG) grown by rf sputtering on gadolinium gallium garnet substrates. The optical absorption profile measured with magneto-optical absorption spectroscopy shows dual optical transition in the UV-visible frequency region attributed to transitions from the O-2p valence band to the Fe-3d conduction band and from the O-2p valence band to Fe-2p53d6 excitonic states at the Γ-symmetry point of the YIG band structure. The application of a static magnetic field of only 0.6 kOe produces giant Zeeman shifts of ∼100 meV in the YIG band structure and ∼60 meV in the excitonic states corresponding to effective g-factors on the order of 104. The giant Zeeman effects are attributed to changes in energy levels by the large exchange fields of the Fe-3d orbitals during the magnetization process.

Dirac-surface-state-dominated spin to charge current conversion in the topological insulator (Bi[subscript 0.22]Sb[subscript 0.78])[subscript 2]Te[subscript 3] films at room temperature

We report an investigation of the dynamics of the three-magnon splitting process associated with the ferromagnetic resonance (FMR) in films of the insulating ferrimagnet yttrium iron garnet (YIG). The experiments are performed with a 6 μm thick YIG film close to a microstrip line fed by a microwave generator operating in the 2–6 GHz range. The magnetization precession is driven by the microwave rf magnetic field perpendicular to the static magnetic field, and its dynamics is observed by monitoring the amplitude of the FMR absorption peak. The time evolution of the amplitude reveals that if the frequency is lowered below a critical value of 3.3 GHz, the FMR mode pumps two magnons with opposite wave vectors that react back on the FMR, resulting in a nonlinear dynamics of the magnetization. The results are explained by a model with coupled nonlinear equations describing the time evolution of the magnon modes.