Tailored by impurities martin gradhand, 1,2, dmitry v. In solids the spin diffusion is caused by the energyconserving flipflop term of a timeindependent dipolar interaction. We have investigated the electron spin diffusion length at room temperature in bulk ndoped germanium as a function of the doping. Jun 10, 2009 in this note, we show that the latest spin grating measurement of spin helix by koralek et al. This permits polarization differences within the sample to be reduced on a timescale much shorter than relaxation effects. 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. Pdf large spin diffusion length in an amorphous organic. As tm0, ss01n, where n is the number of orientationally inequivalent sites. When combined with damping data, spin diffusion length and spin hall angle can be extracted. A long spin relaxation length in an insulator implies weak spin lattice relaxation 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 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.
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. Direct measurement of the electronic spin diffusion length. Determination of the pt spin diffusion length by spinpumping. As a result, the length l1, the spin diffusion length, over. Temperature dependence of spin diffusion length and spin. Two distinct spin diffusion lengths now characterize spin motion, i.
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. From saha d, holub m, and bhattacharya p 2007 amplification of spincurrent polarization. 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. Infinite spin diffusion length of any spin polarization along. Long spin diffusion length in fewlayer graphene flakes. Spin current, spin accumulation and spin hall effect. These time constants were then used to calculate an average lowerlimit spin diffusion length between chemical groups within the plant cell wall. Furthermore, by using thin perovskite single crystals, we discovered that the spin diffusion length was able to reach 1. Voltages generated during excitation of ferromagnetic resonance from the inverse spin hall effect and anisotropic magnetoresistance effect were investigated with a broadband approach. Spindiffusion lengths in metals and alloys, and spinflipping at metalmetal interfaces. 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. 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.
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. Pdf the thickness, temperature, and composition studies of spin diffusion length sdl and spin hall angle sha are performed by. They can be used to solve for the diffusion coefficient, d. 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. By fitting equation 1 to the experimental data, we obtained. Oct 03, 2006 spin flipping within metals is described by a spin diffusion length,lmsf, where the metal m f or n. 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. Despite their impor tance and much effort devoted to quantifying them, significant inconsistencies in the reported values for the same g iven material exist. A diffusion equation approach to spin diffusion in biomolecules.
Measurement of spin diffusion length in sputtered ni. 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. Spin diffusion length of permalloy using spin absorption in. 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. 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. Spin hall angle and spin diffusion length of permalloy. Spin echoes in the presence of a timedependent field gradient e. Sd spin diffusion length j f n spin polarized current l sd f l sd n ieee transactions on electron devices, vol. Efficient spin transport in a paramagnetic insulator. 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. Determination of the pt spin diffusion length by spin. 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. A long spin relaxation length in an insulator implies weak spinlattice relaxation by. Fedorov, 2peter zahn, and ingrid mertig2,1 1maxplanckinstitut fur mikrostrukturphysik, weinberg 2, d06120 halle, germany.
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. 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. Gate control of the electron spindiffusion length in. The ishe induced charge voltages have opposite signs for ta and pt. 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. Temperature dependence of the magnon spin diffusion length and magnon spin conductivity in the magnetic insulator yttrium iron garnet l. Unwanted spin absorption arises in ferromagnetic electrodes if there is a conductivity mismatch with respect to a nonmagnetic channel, i. Solidstate selective c excitation and spin diffusion. The spin diffusion length can be roughly estimated as follows. Solidstate selective c excitation and spin diffusion nmr. We model magnetotransport measurements, performed at. From saha d, holub m, and bhattacharya p 2007 amplification of spincurrent.
Mattana invited paper abstractinjecting spins into a semiconductor channel and transforming the spin. Spin diffusion in bulk gan measured with mnas spin injector. 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. Imaging of pure spinvalley diffusion current in ws2wse2. 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.
Spin diffusion and injection in semiconductor structures. Spin and phase coherence lengths in inas wires with. Transfer of spin polarization among the same kinds of nuclear spins likespins, for example, protons or c, within a macromolecule or across interacting molecules. Direct measurement of the electronic spin diffusion length in a fully. The two critical length scales in giant magnetoresistive structures are the electron mean free path and the spin diffusion length. Condensed matter physics selfconsistent determination of. Department of physics and astronomy, michigan state university, east lansing, michigan 488242320. Spinflipping within metals is described by a spindiffusion length, l m sf, where the metal m f or n. These two metals have large technological significance due to their low cost. Spin polarized transport as measured by superconducting. Silva, determination of spin hall effect and spin diffusion length of pt from selfconsistent fitting of damping enhancement and inverse spin orbit torque. Temperature dependence of spin diffusion length and spin hall angle in au and pt.
Tailored by impurities martin gradhand,1,2, dmitry v. Large spin accumulation with long spin diffusion length in cu. 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 spin hall angle and spin diffusion length in. Temperature dependences of spindiffusion lengths of cu. However, a diffusion length in a silicon solar cell will typically be. 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. In semiconductor spintronic devices, the semiconductor is usually lightly doped and nondegenerate, and. 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. 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.
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. This thesis will discuss the experiments needed to measure the diffusion coefficient by the spinecho method. Pdf spindiffusion lengths in metals and alloys, and spinflipping. Pdf spin diffusion length and spin hall angle in pd 1. Estimation of spindiffusion length from the magnitude of spin. Direct measurement of the spin diffusion length by andreev. 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. Lightenhanced spin diffusion in hybrid perovskite thin. Estimating spin diffusion length from spin pumping experiments. However, the vertical structures only give limited information about series resistances of magnetic multilayers. Nonlocal charg e tr anspor t mediated by spin diffusion in. Spin relaxation and size effects in cu and al nanowires. 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. Despite their importance and much effort devoted to quantifying them, significant inconsistencies in the reported values for the same given material exist.
Pdf temperature dependence of spin diffusion length and spin. Spin diffusion describes a situation wherein the individual nuclear spins undergo continuous exchange of energy. Spin relaxation and diffusion in disordered organic solids. The temperature dependence of the measured spin diffusion length is found to be correlated with the device magnetoresistance. Temperature dependences of spindiffusion lengths of cu and. Pdf estimation of spindiffusion length from the magnitude. Py are the spin hall angle and the spin diffusion length, a pair of important parameters for py. The length scale over which the traveling electron spin memorizes the initial direction is known as the spin diffusion length, an important measure.
The average distance between collisions is the mean free path. Fast spin echo t 1weighted tr 500 t 2weighted tr 2000. Our results indicate that epitaxial ferromagnetic mnas is a suitable hightemperature spin injector for gan. Spin drift and spin diffusion currents in semiconductors. D the concentration gradient is often called the driving force in diffusion but it is not a force in the mechanistic sense. Cross relaxation and spin diffusion in the proton nmr of. Gilbert damping, spinpump effect, spindiffusion length, fmr linewidth, spin.
The length scale over which the travelling electron spin keeps the memory of its initial orientation is known as the spin diffusion length1,2,3,4,5, which is a critical parameter for many spintronic devices6,7,8,9,10,11,12. 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. Electrical spin injection into high mobility 2d systems. Given a conductivity of 15 or 17 microhmcm for pt reported in the two experiments 14, 15, l mf is calculated as 5. 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. 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. Estimation of spindiffusion length from the magnitude of.
Moreaua department of physics, albion college, albion, michigan 49224 ion c. This method is now recognized to be the most accurate way for the measurement of diffusion. Spin diffusion is a process by which magnetization can be exchanged spontaneously between spins. Hahns spinecho method and suggested another pulse sequence called a 90180 sequence and an improved result was ob tained. Pdf we have studied the spin transport and spin hall effect in gold au and platinum pt using lateral spin valve structures. 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. 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. These two length scales play distinctive but both favorable roles in spin injection. Hot electron spin diffusion in ntype gaas springerlink. Spindiffusion lengths are the characteristic lengths in the. University of groningen temperature dependence of the.
Direct measurement of the electronic spin diffusion length in. Spindiffusion lengths in metals and alloys, and 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. The results of the nlsv measurements are summarized in fig. Spin diffusion length of permalloy using spin absorption.
The magnetization thus diffuses over the length of a single crystal or the length of a crystallite in a polycrystalline substance. A diffusion equation approach to spin diffusion in. Selfconsistent determination of spin hall angle and spin. To simplify this equation some parameters are often combined i i edq 0. Gilbert damping, spin pump effect, spin diffusion length, fmr linewidth, spin. First electrical spin injection into n was demonstrated by johnson and silsbee using a singlecrystalline al bulk bar. Ficks laws of diffusion describe diffusion and were derived by adolf fick in 1855.
Evaluation of spin diffusion length and spin hall angle of. Py are investigated for the first time with spin pumping techniques for a fm. Doping dependence of the electron spin diffusion length in germanium. Moreover,wemeasureand analyze the temperature dependence of the spin hall angle in. We employ the spin absorption technique16, 24 9 in lateral spin valves to extract the spin diffusion length of py, py, as a. Spinflipping within metals is described by a spindiffusion length,lmsf, where the metal m f or n. Ficks first law where d is the diffusion coefficient dx dc j. Lightenhanced spin diffusion in hybrid perovskite thin films. If spin flipping is non negligible in multilayers, characteristic lengths need to be defined.