%AVarela-Manjarres, Jalil%ANikolić, Branislav%BJournal Name: Journal of Physics: Materials; Journal Volume: 6; Journal Issue: 4; Related Information: CHORUS Timestamp: 2023-08-23 10:32:36
%D2023%IIOP Publishing
%JJournal Name: Journal of Physics: Materials; Journal Volume: 6; Journal Issue: 4; Related Information: CHORUS Timestamp: 2023-08-23 10:32:36
%K
%MOSTI ID: 10441072
%PMedium: X
%THigh-harmonic generation in spin and charge current pumping at ferromagnetic or antiferromagnetic resonance in the presence of spin–orbit coupling
%XAbstract
One of the cornerstone effects in spintronics is spin pumping by dynamical magnetization that is steadily precessing (around, for example, thez-axis) with frequencyω_{0}due to absorption of low-power microwaves of frequencyω_{0}under the resonance conditions and in the absence of any applied bias voltage. The two-decades-old ‘standard model’ of this effect, based on the scattering theory of adiabatic quantum pumping, predicts that component${I}^{{S}_{z}}$of spin current vector$({I}^{{S}_{x}}(t),{I}^{{S}_{y}}(t),{I}^{{S}_{z}})\propto {\omega}_{0}$is time-independent while${I}^{{S}_{x}}(t)$and${I}^{{S}_{y}}(t)$oscillate harmonically in time with a single frequencyω_{0}whereas pumped charge current is zero$I\equiv 0$in the same adiabatic$\propto {\omega}_{0}$limit. Here we employ more general approaches than the ‘standard model’, namely the time-dependent nonequilibrium Green’s function (NEGF) and the Floquet NEGF, to predict unforeseen features of spin pumping: namely precessing localized magnetic moments within a ferromagnetic metal (FM) or antiferromagnetic metal (AFM), whose conduction electrons are exposed to spin–orbit coupling (SOC) of either intrinsic or proximity origin, will pump both spin${I}^{{S}_{\alpha}}(t)$and chargeI(t) currents. All four of these functions harmonically oscillate in time at both even and odd integer multiples$N{\omega}_{0}$of the driving frequencyω_{0}. The cutoff order of such high harmonics increases with SOC strength, reaching${N}_{\mathrm{m}\mathrm{a}\mathrm{x}}\simeq 11$in the one-dimensional FM or AFM models chosen for demonstration. A higher cutoff${N}_{\mathrm{m}\mathrm{a}\mathrm{x}}\simeq 25$can be achieved in realistic two-dimensional (2D) FM models defined on a honeycomb lattice, and we provide a prescription of how to realize them using 2D magnets and their heterostructures.

%0Journal Article