Engineering of spin mixing conductance at Ru/FeCo/Ru interfaces: Effect of Re doping

Abstract

We have deposited polycrystalline Re doped (F e65Co35)100−xRex (0 ≤ x ≤ 12.6 at%) thin films grown under identical conditions and sandwiched between thin layers of Ru in order to study the phenomenon of spin pumping as a function of Re concentration. In-plane and out-of-plane ferromagnetic resonance spectroscopy results show an enhancement of the Gilbert damping with an increase in Re doping. We found evidence of an increase in the real part of effective spin mixing conductance [Re(g ↑↓ ef f )] with the increase in Re doping of 6.6 at%, while a decrease is evident at higher Re doping. The increase in Re(g ↑↓ ef f ) can be linked to the Re doping induced change of the interface electronic structure in the non-magnetic Ru layer and the effect interfacial spin-orbit coupling has on the effective spin-mixing conductance. The lowest and highest values of Re(g ↑↓ ef f ) are found to be 9.883(02) nm −2 and 19.697(02) nm −2 for 0 at% and 6.6 at% Re doping, respectively. The saturation magnetization decreases with increasing Re doping, from 2.362(13) T for the undoped film to 1.740(03) T for 12.6 at% Re doping. This study opens a new direction of tuning the spin-mixing conductance in magnetic heterostructures by doping of the ferromagnetic layer, which is essential for the realization of energy efficient operation of spintronic devices.

Direct evidence of superdiffusive terahertz spin current arising from ultrafast demagnetization process

“…The asymmetry is ∼10% and ∼4% at the M 2,3 -absorption edge of Fe (∼54 eV) and Co (∼60 eV), respectively. The asymmetry is reduced with increasing Re doping following the same trend as the saturation magnetization, which has already been reported [31,33]. An additional large asymmetry is observed around 44 eV (grey region), which corresponds to the Ru N 2,3 -absorption edge.…”

“…Layers of Ru(3 nm) and Cu(5 nm) were used as seed and capping layers. The nominal thickness of Fe 65 Co 35 was 20 nm, which was verified by x-ray reflectometry [31]. The distribution of the doping element within the films was characterized by Rutherford backscattering.…”

“…We have utilized the Ru layer as a detector of spin polarized currents emanating from a doped Fe 65 Co 35 layer upon ultrafast demagnetization. We have doped the Fe 65 Co 35 layer with different concentrations of the 5d element Re, which has been shown to have a significant effect on the Gilbert damping parameter [31]. We have shown that Re doping of Fe 65 Co 35 decreases the amount of spin accumulation in the Ru layer.…”

“…Previously, it has been shown that the damping parameter of transition-metal films can be modified by introducing 4d, 5d or rare-earth dopants [32,[51][52][53]. Specifically, α increases more than four-fold for 12.6% Re doping in FeCo [31]. In models based on spin pumping through magnon damping [27,29,30] more Gilbert damping would imply an increasing loss of spin angular momentum and a spin voltage imbalance building up at the FeCo/Ru interface, leading to a larger spin current pumped into Ru.…”

Nuclear resonance reflectivity from a [57Fe/Cr]30multilayer with the Synchrotron Mössbauer Source

“…The natural perfect collimation and brightness of SR allowed for measurements of the reflected intensity over a large angular scale. The detection of periodicity in magnetic multilayers (or isotopic periodicity) became possible by observation of the 'magnetic' or 'isotopic' maxima on the NRR angular curve (Chumakov et al, 1993;Toellner et al, 1995;Deá k et al, 1999;Gupta et al, 2005Gupta et al, , 2008Rennhofer et al, 2006;Diederich et al, 2007;Andreeva et al, 2015). The NRR curves were measured using the time gating, i.e.…”