Long-range FMR driven spin pumping through a nonmagnetic insulator (original) (raw)
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Tunable long-distance spin transport in a crystalline antiferromagnetic iron oxide
Nature, 2018
Spintronics uses spins, the intrinsic angular momentum of electrons, as an alternative for the electron charge. Its long-term goal is in the development of beyond-Moore low dissipation technology devices. Recent progress demonstrated the long-distance transport of spin signals across ferromagnetic insulators 1. Antiferromagnetically ordered materials are however the most common class of magnetic materials with several crucial advantages over ferromagnetic systems. In contrast to the latter, antiferromagnets exhibit no net magnetic moment, which renders them stable and impervious to external fields. In addition, they can be operated at THz frequencies 2,3. While fundamentally their properties bode well for spin transport, previous indirect observations indicate that spin transmission through antiferromagnets is limited to short distances of a few nanometers 4-8. Here we demonstrate the long-distance, over tens of micrometers, propagation of spin currents through hematite (α-Fe2O3) 9,10 , the most common antiferromagnetic iron oxide, exploiting the spin Hall effect for spin injection. We control the spin current flow by the interfacial spin-bias 11 and by tuning the antiferromagnetic resonance frequency with an external magnetic field 11. This simple antiferromagnetic insulator is shown to convey spin information parallel to the compensated moment (Néel order) over distances exceeding tens of micrometers. This newlydiscovered mechanism transports spin as efficiently as the net magnetic moments in the bestsuited complex ferromagnets 1. Our results pave the way to ultra-fast, low-power antiferromagnetinsulator-based spin-logic devices that operate at room temperature and in the absence of magnetic fields.
The use of the spin Hall effect and its inverse to electrically detect and manipulate dynamic spin currents generated via ferromagnetic resonance (FMR) driven spin pumping has enabled the investigation of these dynamically injected currents across a wide variety of ferromagnetic materials. However, while this approach has proven to be an invaluable diagnostic for exploring the spin pumping process it requires strong spin-orbit coupling, thus substantially limiting the materials basis available for the detector/channel material (primarily Pt, W and Ta). Here, we report FMR driven spin pumping into a weak spinorbit channel through the measurement of a spin accumulation voltage in a Si-based metaloxide-semiconductor (MOS) heterostructure. This alternate experimental approach enables the investigation of dynamic spin pumping in a broad class of materials with weak spin-orbit coupling and long spin lifetime while providing additional information regarding the phase evolution of the injected spin ensemble via Hanle-based measurements of the effective spin lifetime.
Unconventional Spin Pumping and Magnetic Damping in an Insulating Compensated Ferrimagnet
Advanced Materials, 2022
Recently, the interest in spin pumping has escalated from ferromagnets into antiferromagnetic systems, potentially enabling fundamental physics and magnonic applications. Compensated ferrimagnets are considered alternative platforms for bridging ferroand antiferromagnets, but their spin pumping and the associated magnetic damping have been largely overlooked so far despite their seminal importance for magnonics. Herein, we report an unconventional spin pumping together with magnetic damping in an insulating compensated ferrimagnet Gd3Fe5O12. Remarkably, we unambiguously identified the divergence of the nonlocal effective magnetic damping induced by spin pumping close to the compensation temperature in Gd3Fe5O12/Cu/Pt heterostructures. Furthermore, the coherent and incoherent spin currents, generated by spin pumping and spin Seebeck effect respectively, undergo a distinct direction change with the variation of temperature. The physical mechanisms underlying these observations are self-consistently clarified by the ferrimagnetic counterpart of spin pumping and the handedness-related spin-wave spectra. Our findings broaden the conventional paradigm of the ferromagnetic spin pumping model and open new opportunities for exploring the ferrimagnetic magnonic devices.
Spin pumping in magnetic trilayer structures with an MgO barrier
Scientific Reports, 2016
We present a study of the interaction mechanisms in magnetic trilayer structures with an MgO barrier grown by molecular beam epitaxy. The interlayer exchange coupling, A ex , is determined using SQUID magnetometry and ferromagnetic resonance (FMR), displaying an unexpected oscillatory behaviour as the thickness, t MgO , is increased from 1 to 4 nm. Transmission electron microscopy confirms the continuity and quality of the tunnelling barrier, eliminating the prospect of exchange arising from direct contact between the two ferromagnetic layers. The Gilbert damping is found to be almost independent of the MgO thickness, suggesting the suppression of spin pumping. The element-specific technique of x-ray detected FMR reveals a small dynamic exchange interaction, acting in concert with the static interaction to induce coupled precession across the multilayer stack. These results highlight the potential of spin pumping and spin transfer torque for device applications in magnetic tunnel junctions relying on commonly used MgO barriers.
Spin pumping during the antiferromagnetic–ferromagnetic phase transition of iron–rhodium
Nature Communications, 2020
FeRh attracts intensive interest in antiferromagnetic (AFM) spintronics due to its first-order phase transition between the AFM and ferromagnetic (FM) phase, which is unique for exploring spin dynamics in coexisting phases. Here, we report lateral spin pumping by which angular momentum is transferred from FM domains into the AFM matrix during the phase transition of ultrathin FeRh films. In addition, FeRh is verified to be both an efficient spin generator and an efficient spin sink, by electrically probing vertical spin pumping from FM-FeRh into Pt and from Py into FeRh, respectively. A dramatic enhancement of damping related to AFM-FeRh is observed during the phase transition, which we prove to be dominated by lateral spin pumping across the FM/AFM interface. The discovery of lateral spin pumping provides insight into the spin dynamics of magnetic thin films with mixed-phases, and the significantly modulated damping advances its potential applications, such as ultrafast spintronics.
Spin Orbit Coupling Controlled Spin Pumping and Spin Hall Magnetoresistance Effects
Advanced Electronic Materials, 2016
Effective spin mixing conductance (ESMC) across the nonmagnetic metal (NM)/ferromagnet interface, spin Hall conductivity (SHC), and spin diffusion length (SDL) in the NM layer govern the functionality and performance of pure spin current devices. It is shown that all three parameters can be tuned significantly via the spin orbit coupling (SOC) strength of the NM layer by virtue of the unique Pd1‐xPtx/Y3Fe5O12 system. Surprisingly, the ESMC is observed to increase significantly with x changing from 0 to 1.0, due to the enhanced local density of states for Pt‐rich alloys. The SHC in PdPt alloys turns out to be dominated by the skew scattering term. In particular, the skew scattering parameter has for the first time been rigorously demonstrated to increase with increasing SOC strength. Meanwhile, the SDL is found to decrease when Pd atoms are replaced by heavier Pt atoms, validating the SOC induced spin flip scattering model in polyvalent PdPt alloys. A thorough grasp of the dependence...
Spin injection with small ferromagnetic metal
Journal of Magnetism and Magnetic Materials, 2005
We present a design for spin injection from a ferromagnetic (FM)-nonmagnetic (NM) bilayer into a semiconductor (SC) layer. This device consists of a left bilayer injector, the SC layer and a right bilayer collector. The FM has a much smaller cross-sectional area (A) compared to the device. This increases the spin-dependent resistance as a fraction of the total device resistance and reduces the effect of conductivity mismatch which suppresses spin-injection efficiency. The NM layer is required as a buffer to contain the spreading resistance (R SP) that arises from the discontinuity of A. With Ni 80 Fe 20 /Cu as the bilayers, and GaAs as the SC, our computation yields a spin-injection efficiency of 20% for doping density N D of 10 18 cm À3 , which rises to 30% for N D ¼ 10 20 cm À3 :