|
It was recently reported that THz emission can be realized in ferromagnetic (FM) /non-FM bilayers via dynamical spin-to charge conversion originating from interfacial spin-orbit coupling or inverted spin-Hall effect (ISHE) [1-3]. We will present our results of THz emission provided by optimized grownth bilayers composed of a high-spin orbit material (Pt, Au :W) in contact with a thin ferromagnetic layer Co/Pt, NiFe/Au:W, NiFe/Au:Ta. Those bilayers are used in experiments combining RF-spin pumping and spin-to-charge conversion by ISHE [4-5]. In comparaison with Co/Pt systems, in NiFe/Au:Ta and NiFe/Au:W bilayers provide a smaller signal even though the spin Hall angles for Au:Ta and Au:W are larger than for Pt [6]. This is mainly due to their smaller spin-mixing conductance in comparaison with Co/Pt. We will discuss the role of the generalized spin-mixing conductance on the spin-transport properties and spin-orbit torques involved in the time-dependent diffusion and relaxation phenomena. We demonstrate that the THz signals strongly depend on the spin Hall angle of non-FM metal, spin diffusion length, and spin-mixing conductance. In the structures with large spin-mixing conductance and spin length diffusion, e.g., Co/Pt, the THz signal is comparable to ZnTe signal. It should be a rapid method to know the characteristic of spintronics samples. We have also studied in the static regime the unconventional Anomalous Hall effect (AHE) of Pt/[CoNi]_N multilayers showing up a characteristic AHE spin-inversion from Pt to Au:W samples by proximity effect. We analyze our results in the series of samples: the exact conductivity profile across the multilayers via the 'extended' Camley-Barnas approach [7] and the spin current profile generated by SHE. The values of spin Hall angles in layers are found: -0.2 for Pt (enhanced compared to CPP geometry)In [Co,Ni]N/Pt sample, we show that the transverse current changes from negative (N<20) to positive (N>20) values.
[1] T. J. Huisman et al., Nat.Nano 11, 455–458 (2016)
[2] T. Seifert et al., Nat.Photo 10, 483-488 (2016)
[3] D. Yang et al., Adv.Opt.Mat. 4, 1944-1949 (2016)
[4] J.C Rojas-Sanchez et al., PRL. 112, 106602 (2014)
[5] P. Laczowski et al, APL 104, 142403 (2014)
[6]P. Laczowski et al, Phys. Rev. B 96, 140405(R) (2017)
[7] R. E. Camley et al., Phys. Rev. Lett. 63, 664 (1989); J. Barnas et al., Phys. Rev. B 42, 8110 (1990)
|
