Throughout my scientific career, I have co-authored more than 20 papers published in scientific journals, collaborating with over 40 authors from 20 different institutions. I regularly review manuscripts for scientific journals, including Physical Review Letters, Physical Review B, Physical Review Applied, Nature Communications, and Applied Physics Letters.

Research areas of interest are listed below:

Magnonic nanodevices

Magnons are the quanta of spin waves in magnetic systems. These spin waves are disturbances in the alignment of spins that propagate through the magnetic material, similar to waves on a lake. Magnons have the ability to transmit spin angular momentum, or spin current, in the absence of charge motion, thereby suppressing dissipation due to Joule heating. Consequently, magnonic devices aim to exploit spin and magnon effects to transmit or process (quantum) information, offering significant energy advantages. There are still major gaps in the understanding of how magnons are excited and propagate in different materials.

Ilustration of a magnon transport experiment on YIG. Magnons are excited via Inverse Spin Hall Effect (ISHE) on platinum strips.

O. Alves Santos and B. J. van Wees, Magnon confinement in an all-on-chip yig cavity resonator using hybrid YIG/Py magnon barriers, Nano Letters 23, 9303 (2023).
X.-Y. Wei, O. Alves Santos, C. S. Lusero, G. Bauer, J. Ben Youssef, and B. Van Wees, Giant magnon spin conductivity in ultrathin yttrium iron garnet films, Nature Materials 21, 1352 (2022).
O. Alves Santos, F. Feringa, K. Das, J. B. Youssef, and B. Van Wees, Efficient modulation of magnon conductivity in Y3Fe5O12 using anomalous spin Hall effect of a permalloy gate electrode, Physical Review Applied 15, 014038 (2021).

Thin film spintronics

Spintronics aims to exploit the electron spin for information processing and storage, thereby adding a new degree of freedom to conventional electronics. Since the electron spin plays a fundamental role in the magnetic properties of materials, various spintronic effects, such as the Spin Pumping effect (SPE), Spin Magnetoresistance (SMR), and Spin Seebeck effect (SSE), can be used as probes for the local study of magnetic systems and in the development of new spin-dependent sensors. I am particularly interested in using these effects to provide novel ways of probing the magnetic properties of materials.

Illustration of SMR. The spin Hall effect (SHE), inject pure spin current into the magnetic layer. The interaction between the spin current and the magnetization provides crucial insights on the magnetic material.

D. Hamara, M. Strungaru, J. R. Massey, Q. Remy, X. Chen, G. Nava Antonio, O. Alves Santos, M. Hehn, R. F. Evans, R. W. Chantrell, et al., Ultra-high spin emission from antiferromagnetic FeRh, Nature Communications 15, 4958 (2024).
O. Alves Santos, E. Silva, M. Gamino, R. Cunha, J. Mendes, R. Rodríguez-Suárez, S. Rezende, and A. Azevedo, Giant spin-charge conversion driven by nanoscopic particles of Ag in Pt, Physical Review B 96, 060408 (2017).
J. Mendes, R. Cunha, O. Alves Santos, P. Ribeiro, F. Machado, R. Rodríguez-Suárez, A. Azevedo, and S. Rezende, Large inverse spin hall effect in the antiferromagnetic metal Ir20Mn80, Physical Review B 89, 140406 (2014).

2D and Quantum materials

The conversion of spin current into charge current can occur in two-dimensional materials due to the Rashba–Edelstein effect. This effect arises from symmetry breaking at interfaces, generating a local electric field, known as the Rashba field. Often, this field is induced by proximity effects between the two-dimensional material and adjacent materials. This phenomenon results in coupling between the electron spin and momentum. In this research area, I maintain a strong collaboration with Prof. Joaquim Mendes, and Prof. Rafael Otoniel, from UFV.

It was a important achievement in measuring the spin pumping effect in Graphene, as well as the directly measuring the magnetoresistance of YIG/SLG. Demonstrating the strong coupling between free electrons in graphene and the YIG magnetization, resulting from the proximity effect and the Inverse Rashba-Edelstein effect.

J. Mendes, O. Alves Santos, J. Holanda, R. P. Loreto, C. De Araujo, C.-Z. Chang, J. Moodera, A. Azevedo, and S. Rezende, Dirac-surface-state-dominated spin to charge current conversion in the topological insulator BiSbTe films at room temperature, Physical Review B 96, 180415 (2017).
J. Mendes, O. Alves Santos, L. Meireles, R. Lacerda, L. Vilela-Leão, F. Machado, R. Rodríguez-Suárez, A. Azevedo, and S. Rezende, Spin-current to charge-current conversion and magnetoresistance in a hybrid structure of Graphene and Yttrium Iron Garnet, Physical Review Letters 115, 226601 (2015).

Electron Paramagnetic Resonance (EPR) and FMR

As coordinator of LabEPR (Laboratório Multiusuário de Ressonância Paramagnética Eletrônica) at CBPF, I am deeply committed to sharing my expertise in FMR and EPR spectroscopy to study a wide variety of materials. These techniques are versatile tools that provide crucial insights into the electronic and magnetic properties of matter and play a central role in solid-state physics, biophysics, and chemistry, enabling the investigation of paramagnetic centers, spin dynamics, and molecular structures.

More details on LabEPR website. Link below.

LabEPR website

Comon EPR signal (Bruker - EMXPlus).