Roadmap for the Design of All Ferromagnetic Four-Terminal Spin Valves and the Extraction of Spin Diffusion Length

Abstract

Graphene is a promising substrate for future spintronics devices owing to its remarkable electronic mobility and low spin-orbit coupling. Hanle precession in spin valve devices is commonly used to evaluate the spin diffusion and spin lifetime properties. In this work, we demonstrate that this method is no longer accurate when the distance between inner and outer electrodes is smaller than six times the spin diffusion length, leading to errors as large as 50% for the calculations of the spin figures of merit of graphene. We suggest simple but efficient approaches to circumvent this limitation by addressing a revised version of the Hanle fit function. Complementarily, we provide clear guidelines for the design of four-terminal spin valves able to yield flawless estimations of the spin lifetime and the spin diffusion coefficient.

Organic–Inorganic Hybrid Interfaces for Spin Injection into Carbon Nanotubes and Graphene

“…This lets open clear perspectives for further enhancement of graphene spin transport properties exploitation. [ 119,121 ]…”

“…This lets open clear perspectives for further enhancement of graphene spin transport properties exploitation. [119,121] In this direction, focusing on multilayer graphene grown epitaxially on SiC, Dlubak et al [123] have investigated spin transport in a highly confined device configuration, where multilayer graphene shields the inner transport channels which are further strictly limited to the space between the two spin-polarized tunnel electrodes (see Figure 4d). This has been deemed the optimal configuration to reach the intrinsic properties of the channel.…”

“…[14,21] It has also been discussed that transport properties in a device with tunnel contacts but with extended channel and multiple contacts can be detrimental to the spin signal. [62,119] Illustratively, a leaky contact deposited on the channel, even if located further away from the probed area, can act as a strong spin-sink for the device properties, [120] while this situation has been neither discussed or even less systematically analyzed in the literature. This lets open clear perspectives for further enhancement of graphene spin transport properties exploitation.…”

CVD Bilayer Graphene Spin Valves with 26 μm Spin Diffusion Length at Room Temperature

“…However, the fact that the resulting spin diffusion lengths are comparable to the device dimensions (compare to Figure e) seemingly contradicts a fundamental assumption in the aforementioned derivation of the fit function: The outer electrodes are assumed to be placed in a region of the device in which the induced spin accumulation of the inner injection electrode is reduced to a negligible level by relaxation processes. Recent studies have predicted that otherwise our used fitting function yields erroneous results for both the fitted spin lifetime and spin diffusion length. − …”