The nonlocal spin injection in lateral spin valves is highly expected to be an effective method to generate a pure spin current for potential spintronic application. However, the spin valve voltage, which decides the magnitude of the spin current flowing into an additional ferromagnetic wire, is typically of the order of 1 μV. Here we show that lateral spin valves with low resistive NiFe/MgO/Ag junctions enable the efficient spin injection with high applied current density, which leads to the spin valve voltage increased hundredfold. Hanle effect measurements demonstrate a long-distance collective 2π spin precession along a 6 μm long Ag wire. These results suggest a route to faster and manipulable spin transport for the development of pure spin current based memory, logic and sensing devices.

Devices based on pure spin currents have been attracting increasing attention as key ingredients for low-dissipation electronics. To integrate such spintronics devices into chargebased technologies, electric detection of spin currents is essential. The inverse spin Hall effect converts a spin current into an electric voltage through spin-orbit coupling. Noble metals such as Pt and Pd, and also Cu-based alloys, have been regarded as potential materials for a spincurrent injector, owing to the large direct spin Hall effect. Their spin Hall resistivity r SH , representing the performance as a detector, is not large enough, however, due mainly because of their low charge resistivity. Here we report that a binary 5d transition metal oxide, iridium oxide, overcomes the limitations encountered in noble metals and Cu-based alloys and shows a very large r SH B38 mO cm at room temperature.

We experimentally confirmed that the spin-orbit lengths of noble metals obtained from weak antilocalization measurements are comparable to the spin diffusion lengths determined from lateral spin valve ones. Even for metals with strong spin-orbit interactions such as Pt, we verified that the two methods gave comparable values which were much larger than those obtained from recent spin torque ferromagnetic resonance measurements. To give a further evidence for the comparability between the two length scales, we measured the disorder dependence of the spin-orbit length of copper by changing the thickness of the wire. The obtained spin-orbit length nicely follows a linear law as a function of the diffusion coefficient, clearly indicating that the Elliott-Yafet mechanism is dominant as in the case of the spin diffusion length.

We have systematically investigated the interface contributions to the spin injection characteristics in permalloy/MgO/Ag lateral spin valves. The spin valve signal remarkably increases with MgO thickness and reaches a maximum when the interface resistance is about 100 f⍀ m 2 for 1 nm thick MgO, which is two orders of magnitude lower than that of the typical tunnel junction. Our quantitative analysis based on the spin-dependent diffusion equation considering variable spin polarization in the MgO layer well describes the observed trend in the spin valve signals.

Spin-flip mechanism in Ag nanowires with MgO surface protection layers has been investigated by means of nonlocal spin valve measurements using Permalloy/Ag lateral spin valves. The spin flip events mediated by surface scattering are effectively suppressed by the MgO capping layer. The spin relaxation process was found to be well described in the framework of Elliott-Yafet mechanism and then the probabilities of spin-filp scattering for phonon or impurity mediated momentum scattering is precisely determined in the nanowires. The temperature dependent spin-lattice relaxation follows the Bloch-Grüneisen theory and falls on to a universal curve for the monovalent metals as in the Monod and Beuneu scaling determined from the conduction electron spin resonance data for bulk.Spin injection, transport and detection are key ingredients in spintoronics, which have drawn a great deal of attention in recent years due to possible application for magnetic memories as well as fundamental interests concerning the interplay between charge and spin transport. 1,2 Lateral spin valves (LSVs) offer an effective means to study transport properties of a pure spin current, i.e., a diffusive flow of spin angular momentum accompanying no charge currents. A large number of the spin injection experiments have been reported since the pioneering work by Johnson and Silsbee in 1985. 3 More recently non-local spin valve experiments by Jedema et al. 4 brought renewed interests in LSVs in response to the timely development in both micro-fabrication technology and emergent interest in the pure spin current. Having a betterinsight into the spin transport and relaxation mechanism in nano-scaled devices is important to enhance the performance for the spintronic application.The spin relaxation mechanism in nonmagnetic metals (NM) has originally been discussed by Elliott and Yafet. 5,6 According to their theory, the spin-orbit interaction (SOI) in NM lifts the spin degeneracy of Bloch electrons, and results in two different energy states for up or down spin.The spin relaxation, i.e., the transition between the opposite spin states, can therefore be caused by the spin independent momentum scatterings due to impurities, grain boundaries, surfaces and phonon. [5][6][7] The earlier experimental works on the spin relaxation mechanism were mainly performed by conduction electron spin resonance (CESR) measurements and the results were

A long spin relaxation time (τ sf ) is the key for the applications of graphene to spintronics but the experimental values of τ sf have been generally much shorter than expected. We show that the usual determination by the Hanle method underestimates τ sf if proper account of the spin absorption by contacts is lacking. By revisiting series of experimental results, we find that the corrected τ sf are longer and less dispersed, which leads to a more unified picture of τ sf derived from experiments. We also discuss how the correction depends on the parameters of the graphene and contacts.

We have succeeded in fully describing dynamic properties of spin current including the different spin absorption mechanism for longitudinal and transverse spins in lateral spin valves, which enables to elucidate intrinsic spin transport and relaxation mechanism in the nonmagnet.The deduced spin lifetimes are found independent of the contact type. From the transit-time distribution of spin current extracted from the Fourier transform in Hanle measurement data, the velocity of the spin current in Ag with Py/Ag Ohmic contact turns out much faster than that expected from the widely used model.

That one can stack van der Waals materials with atomically sharp interfaces has provided a new material platform of constructing heterostructures. The technical challenge of mechanical stacking is picking up the exfoliated atomically thin materials after mechanical exfoliation without chemical and mechanical degradation. Chemically inert hexagonal boron nitride (hBN) has been widely used for encapsulating and picking up vdW materials. However, due to the relatively weak adhesion of hBN, assembling vdW heterostructures based on hBN has been limited. We report a new dry transfer technique. We used two vdW semiconductors (ZnPS 3 and CrPS 4 ) to pick up and encapsulate layers for vdW heterostructures, which otherwise are known to be hard to fabricate. By combining with optimized polycaprolactone (PCL) providing strong adhesion, we demonstrated various vertical heterostructure devices, including quasi-2D superconducting NbSe 2 Josephson junctions with atomically clean interface. The versatility of the PCL-based vdW stacking method provides a new route for assembling complex 2D vdW materials without interfacial degradation.