Estimating spin diffusion length from spin pumping experiments. A long spin relaxation length in an insulator implies weak spin lattice relaxation by. Spin hall angle and spin diffusion length of permalloy. These two metals have large technological significance due to their low cost. A linear dependence of the spin diffusion length with conductivity of py is observed, evidencing that elliottyafet is the dominant spin relaxation mechanism in. The spin diffusion length is the length over which the polarization of the electron current is destroyed owing to spin flip scattering. Sep 20, 2018 the spin diffusion length of a giant spin orbit material platinum pt has been reported in literature in a wide range of 0. Spin polarized transport as measured by superconducting. Given a conductivity of 15 or 17 microhmcm for pt reported in the two experiments 14, 15, l mf is calculated as 5.
Fedorov, 2peter zahn, and ingrid mertig2,1 1maxplanckinstitut fur mikrostrukturphysik, weinberg 2, d06120 halle, germany. Dec 12, 20 the spin diffusion length of pt at room temperature and at 8 k is experimentally determined via spin pumping and spin hall effect in permalloypt bilayers. Temperature dependence of the magnon spin diffusion length and magnon spin conductivity in the magnetic insulator yttrium iron garnet l. Selfconsistent determination of spin hall angle and spin. Electrical spin injection into high mobility 2d systems. Py are investigated for the first time with spin pumping techniques for a fm. Ficks laws of diffusion describe diffusion and were derived by adolf fick in 1855. Imaging of pure spinvalley diffusion current in ws2wse2. Measurement of spin diffusion length in sputtered ni. Pdf temperature dependence of spin diffusion length and spin. We model magnetotransport measurements, performed at. Spinflipping within metals is described by a spindiffusion length, l m sf, where the metal m f or n. Estimation of spindiffusion length from the magnitude of spin. Spin relaxation and size effects in cu and al nanowires.
Ficks first law can be used to derive his second law which in turn is identical to the diffusion equation a diffusion process that obeys ficks laws is called normal diffusion or fickian diffusion. Spin current, spin accumulation and spin hall effect. Condensed matter physics selfconsistent determination of. The spin diffusion length can be roughly estimated as follows. Ficks first law where d is the diffusion coefficient dx dc j. Lightenhanced spin diffusion in hybrid perovskite thin films. Tanner department of chemistry, university of wisconsin, madison, wisconsin received 20 july 1964 a derivation is given of the effect of a timedependent magnetic field gradient on the spin echo experiment. The ishe induced charge voltages have opposite signs for ta and pt. The spin diffusion length of pt at room temperature and at 8 k is experimentally determined via spin pumping and spin hall effect in permalloypt bilayers. Sd spin diffusion length j f n spin polarized current l sd f l sd n ieee transactions on electron devices, vol. Pdf spindiffusion lengths in metals and alloys, and spinflipping. The average distance between collisions is the mean free path.
Kimmich and noack46 claim that this assumption may be incorrect for proton spinlattice relaxation because of spin diffusion, but clear evidence of spin diffusion in hydrated biological. Spindiffusion lengths in metals and alloys, and spinflipping at metalmetal interfaces. However, a diffusion length in a silicon solar cell will typically be. Voltages generated during excitation of ferromagnetic resonance from the inverse spin hall effect and anisotropic magnetoresistance effect were investigated with a broadband approach. Large spin accumulation with long spin diffusion length in cu. Hot electron spin diffusion in ntype gaas springerlink. Condensed matter physics selfconsistent determination. Consider that, upon entering the nonmagnetic material from the fm, any given electron will undergo a number of collisions say, n before flipping its spin. Using this drift diffusion model, we deduce expressions for the spin drift and spin diffusion current densities and show that the extension of the spin diffusion length by a strong electric field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion, which is. Despite their impor tance and much effort devoted to quantifying them, significant inconsistencies in the reported values for the same g iven material exist.
Efficient spin transport in a paramagnetic insulator. Oct 03, 2006 spin flipping within metals is described by a spin diffusion length,lmsf, where the metal m f or n. Pdf estimation of spindiffusion length from the magnitude. When combined with damping data, spin diffusion length and spin hall angle can be extracted. Spin diffusion in bulk gan measured with mnas spin injector. Doping dependence of the electron spin diffusion length in germanium. Gilbert damping, spin pump effect, spin diffusion length, fmr linewidth, spin. Solidstate selective c excitation and spin diffusion nmr. Spin relaxation in gan is interpreted in terms of the dyakonovperel mechanism, yielding a maximum spin lifetime of 44 ps and a spin diffusion length of 175 nm at room temperature. Solidstate selective c excitation and spin diffusion.
The spinup and spindown currents flow in opposite directions in contact pad d2, yielding spin polarization gain greater than unity, b estimated spindiffusion length as a function of temperature. Direct measurement of the electronic spin diffusion length in a fully. Pdf large spin diffusion length in an amorphous organic. This rather long spin diffusion length led to the proposal of a spin injection technique using a f1nf2 structure f1 is an injector and f2 a. This occurs as a result of dipolar coupling among likespins, when they are densely packed in relative proximity within a few to several angstroms distance in space. Despite their importance and much effort devoted to quantifying them, significant inconsistencies in the reported values for the same given material exist. Spin diffusion length of permalloy using spin absorption. Determination of spin hall angle and spin diffusion length in.
This method is now recognized to be the most accurate way for the measurement of diffusion. Two distinct spin diffusion lengths now characterize spin motion, i. The results of the nlsv measurements are summarized in fig. Spin diffusion is a process by which magnetization can be exchanged spontaneously between spins. Silva, determination of spin hall effect and spin diffusion length of pt from selfconsistent fitting of damping enhancement and inverse spin orbit torque. A diffusion equation approach to spin diffusion in. Pdf we have studied the spin transport and spin hall effect in gold au and platinum pt using lateral spin valve structures. Pdf spin diffusion length and spin hall angle in pd 1.
University of groningen temperature dependence of the. Spin hall angle q sh and spin diffusion length l sd are the key parameters in describing the spin charge conversion, which is an integral part of spintronics. These time constants were then used to calculate an average lowerlimit spin diffusion length between chemical groups within the plant cell wall. This thesis will discuss the experiments needed to measure the diffusion coefficient by the spinecho method. Evaluation of spin diffusion length and spin hall angle of.
Fast spin echo t 1weighted tr 500 t 2weighted tr 2000. Sep 20, 20 the length scale over which the travelling electron spin keeps the memory of its initial orientation is known as the spin diffusion length 1,2,3,4,5, which is a critical parameter for many. To simplify this equation some parameters are often combined i i edq 0. Spin and phase coherence lengths in inas wires with. In solids the spin diffusion is caused by the energyconserving flipflop term of a timeindependent dipolar interaction. If spin flipping is non negligible in multilayers, characteristic lengths need to be defined. Temperature dependences of spindiffusion lengths of cu and. However, the vertical structures only give limited information about series resistances of magnetic multilayers. Mattana invited paper abstractinjecting spins into a semiconductor channel and transforming the spin. The length scale over which the travelling electron spin keeps the memory of its initial orientation is known as the spindiffusion length 1,2,3,4,5, which is a critical parameter for many. They can be used to solve for the diffusion coefficient, d. In semiconductor spintronic devices, the semiconductor is usually lightly doped and nondegenerate, and.
Spin diffusion describes a situation wherein the individual nuclear spins undergo continuous exchange of energy. We employ the spin absorption technique in lateral spin valves to extract the spin diffusion length of permalloy py as a function of temperature and resistivity. Unwanted spin absorption arises in ferromagnetic electrodes if there is a conductivity mismatch with respect to a nonmagnetic channel, i. Kimmich and noack46 claim that this assumption may be incorrect for proton spin lattice relaxation because of spin diffusion, but clear evidence of spin diffusion in hydrated biological. We systematically measure and analyze the spin diffusion length and the spin hall effect in pt with a wide range of conductivities using the spin absorption method in lateral spin valve devices. Spindiffusion lengths in metals and alloys, and spin. Temperature dependences of spindiffusion lengths of cu. Pdf we performed ab initio studies to search for materials where a large spin hall effect caused by skew scattering is accompanied by a long spin. A linear dependence of the spin diffusion length with conductivity of py is observed, evidencing that elliottyafet is the dominant spin relaxation mechanism in permalloy. Furthermore, by using thin perovskite single crystals, we discovered that the spin diffusion length was able to reach 1. On the basis of a spin drift diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant. Spindiffusion lengths are the characteristic lengths in the. Temperature dependence of spin diffusion length and spin. From saha d, holub m, and bhattacharya p 2007 amplification of spincurrent.
Our results indicate that epitaxial ferromagnetic mnas is a suitable hightemperature spin injector for gan. We employ the spin absorption technique16, 24 9 in lateral spin valves to extract the spin diffusion length of py, py, as a function of temperature and resistivity. Estimation of spindiffusion length from the magnitude of. From saha d, holub m, and bhattacharya p 2007 amplification of spincurrent polarization. Transfer of spin polarization among the same kinds of nuclear spins likespins, for example, protons or c, within a macromolecule or across interacting molecules. Temperature dependence of spin diffusion length and spin hall angle in au and pt. Because of the lightresponsive nature of the hybrid perovskite, a high magnetoresistance of 97% and a large spin diffusion length of 81 nm were achieved at 10 k under light illumination in polycrystalline films. Infinite spin diffusion length of any spin polarization along. Tailored by impurities martin gradhand, 1,2, dmitry v. The application of point contact andreev spectroscopy for the measurement of the spin diffusion length is demonstrated by studying the spin relaxation in platinum thin films grown on the top of a. Spinflipping within metals is described by a spindiffusion length,lmsf, where the metal m f or n. Hahns spinecho method and suggested another pulse sequence called a 90180 sequence and an improved result was ob tained. This permits polarization differences within the sample to be reduced on a timescale much shorter than relaxation effects. A diffusion equation approach to spin diffusion in biomolecules.
Direct measurement of the electronic spin diffusion length. Department of physics and astronomy, michigan state university, east lansing, michigan 488242320. Despite their impor tance and much effort devoted to quantifying them, signif icant inconsistencies in the reported values for the same g iven material exist. The diffusivity is a measure of how quickly a group of particles fill a space and it is described in more detail on the diffusion page the diffusivity is typically given in cm 2 s and the lifetime is in seconds so the above formula will give the diffusion length in cm. Determination of the pt spin diffusion length by spinpumping. May 25, 2018 taking advantage of the electrons spin and valley degrees of freedom requires a method for generating currents of carriers that have a particular spin or come from a particular valley in the electronic structure. Taking advantage of the electrons spin and valley degrees of freedom requires a method for generating currents of carriers that have a particular spin or come from a particular valley in the electronic structure. As a result, the length l1, the spin diffusion length, over. Cross relaxation and spin diffusion in the proton nmr of. Tailored by impurities martin gradhand,1,2, dmitry v. The magnetization thus diffuses over the length of a single crystal or the length of a crystallite in a polycrystalline substance. Lightenhanced spin diffusion in hybrid perovskite thin. By fitting equation 1 to the experimental data, we obtained. Pdf the thickness, temperature, and composition studies of spin diffusion length sdl and spin hall angle sha are performed by.
Large spin accumulation with long spin diffusion length in cumgopermalloy lateral spin valves taro wakamura 1, kohei ohnishi, yasuhiro niimi, and yoshichika otani. The journal of photonics for energy jpe covers fundamental and applied research areas focused on the applications of photonics for renewable energy harvesting, conversion, storage, distribution, monitoring, consumption, and efficient usage. Py are the spin hall angle and the spin diffusion length, a pair of important parameters for py. Spin diffusion length of permalloy using spin absorption in. Gate control of the electron spindiffusion length in. Nonlocal charg e tr anspor t mediated by spin diffusion in. Spin is said to accumulate near the interface, and spin polarization decays exponentially away from the interface due to spin flip scattering events on the scale of what is called the spill diffusion lenght, lsd thus, spin flip scattering events destroy the transport of spin, leading to a characteristic length. Jun 10, 2009 in this note, we show that the latest spin grating measurement of spin helix by koralek et al. Spin drift and spin diffusion currents in semiconductors. As tm0, ss01n, where n is the number of orientationally inequivalent sites.
This small spin diffusion length is incompatible with the fundamental spin diffusion theory, in which the spin diffusion length must be larger than the electron mean free path l mf 22, 23. A long spin relaxation length in an insulator implies weak spinlattice relaxation by. Gilbert damping, spinpump effect, spindiffusion length, fmr linewidth, spin. We have investigated the electron spin diffusion length at room temperature in bulk ndoped germanium as a function of the doping.
Spin relaxation and diffusion in disordered organic solids. Spin echoes in the presence of a timedependent field gradient e. We employ the spin absorption technique16, 24 9 in lateral spin valves to extract the spin diffusion length of py, py, as a. These two length scales play distinctive but both favorable roles in spin injection. Moreover,wemeasureand analyze the temperature dependence of the spin hall angle in. Determination of the pt spin diffusion length by spin. The two critical length scales in giant magnetoresistive structures are the electron mean free path and the spin diffusion length. Direct measurement of the spin diffusion length by andreev. Spin diffusion and injection in semiconductor structures.
Direct measurement of the electronic spin diffusion length in. By variation of the excitation energy and lattice temperature we demonstrate that this discrepancy is caused by the influence of the pumpinduced local overheating of the electron system with respect to the lattice, which persists over length scales comparable to the spin diffusion length. Long spin diffusion length in fewlayer graphene flakes. Moreaua department of physics, albion college, albion, michigan 49224 ion c. First electrical spin injection into n was demonstrated by johnson and silsbee using a singlecrystalline al bulk bar. The length scale over which the traveling electron spin memorizes the initial direction is known as the spin diffusion length, an important measure. D the concentration gradient is often called the driving force in diffusion but it is not a force in the mechanistic sense.
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