Self-Induced Spin Pumping and Inverse Spin Hall Effect in Single FePt Thin Films

• Published in: ACS applied electronic materials 2024-11, Vol.6 (11), p.8298-8308
• Main Authors: Ampuero, José Luis, Anadón, Alberto, Damas, Héloïse, Ghanbaja, Jaâfar, Petit-Watelot, Sébastien, Rojas-Sánchez, Juan-Carlos, Velázquez Rodriguez, Daniel, Gómez, Javier, Butera, Alejandro, Avilés-Félix, Luis
• Format: Article
• Language: English
• ISSN: 2637-6113; 2637-6113
• DOI: 10.1021/acsaelm.4c01555

Self-induced spin Hall effect and self-torque hold great promise in the field of spintronics, offering a path toward highly efficient spin-to-charge interconversion, a pivotal advancement for data storage, sensing devices, or unconventional computing. In this study, we investigate the spin-charge current conversion characteristics of chemically disordered ferromagnetic single FePt thin films by spin-pumping ferromagnetic resonance experiments performed on both a resonance cavity and on patterned devices. We clearly observe a self-induced signal in a single FePt layer. The sign of a single FePt spin pumping voltage signal is consistent with a typical bilayer with a positive spin Hall angle layer such as that of Pt on top of a ferromagnet (FM), substrate//FM/Pt. Structural analysis shows a composition gradient due to natural oxidation at both FePt interfaces, with the Si substrate and with the air. The FePt-thickness dependence of the self-induced charge current produced allowed us to obtain λFePt = (1.5 ± 0.1) nm and self-induced θself‑FePt = 0.047 ± 0.003, with efficiency for reciprocal effects applications θself‑FePt × λFePt = 0.071 nm which is comparable to that of Pt, θSH‑Pt × λPt = 0.2 nm. The spin pumping voltage is also observed in a symmetrical stacking, Al/FePt/Al with a lower overall efficiency. Moreover, by studying bilayer systems such as Si//FePt/Pt and Si//Pt//FePt we independently could extract the individual contributions of the external inverse spin Hall effect of Pt and the self-induced inverse spin Hall effect of FePt. Notably, this method gives consistent values of charge currents produced due to only self-induced inverse spin Hall effect in FePt layers. These results advance our understanding of spin-to-charge interconversion mechanisms in composite thin films and pave the way for the development of next-generation spintronics devices based on self-torque.