Giant spin anomalous Hall effect and ways to exploit the self-spin-orbit torque in ferromagnetic materials

Juan-Carlos Rojas-Sanchez, Université de Lorraine, CNRS

January 29, 2021

In order to address the high demand for data in information technology, spintronics proposes attractive solutions. They are mainly based on the exploitation of the spin-orbit coupling of heavy metals to use the spin-orbit torque (SOT) exerted on the magnetic layers attached to the heavy metal. An example of this concept is presented in the W/CoTb/AlOx system. Here, as the resistivities of the W and CoTb are similar, we introduce a new characteristic temperature, T_switch, which is higher than the magnetic and angular compensation temperatures and lower than the Curie temperature [1].

However, magnetic material can be a source of spin current as well. In GdFeCo, we can identify spin currents of two different symmetries, SAHE-like [2,3] and SHE-like[4] corresponding respectively to the symmetries of the Spin Anomalous Hall Effect and Spin Hall Effect [5]. We report giant SAHE in GdFeCo amorphous ferrimagnetic thin films. Overall efficiency is 25 times more important in GdFeCo/Cu/NiFe than in Pt/Cu/NiFe. Furthermore, we compare the self-torque in GdFeCo/Cu with torques induced by Pt or Ta in Pt/Cu/GdFeCo and Ta/Cu/GdFeCo structures. This paves the way for new architectures to achieve and exploit heavy metal free SOT switching and skyrmions manipulation [5].

[1] Thai-Ha Pham et al. Phys. Rev. Appl. 9, 064032 (2018). ArXiv: 1711.10790
[2] T. Taniguchi et al., Phys. Rev. Appl. 3, 044001 (2015).
[3] S. Ihama et al., Nat. Elecron. 1, 120 (2018).
[4] Amin et al. J. Appl. Phys. 128, 151101 (2020).
[5] David Céspedes-Berrocal et al. Adv. Materials
https://doi.org/10.1002/adma.202007047 (2020). ArXiv: 2010.09137