[en] Graphene is a promising substrate for future spintronic devices owing to its remarkable electronic mobility and low spin-orbit coupling. Hanle precession in spin-valve devices is commonly used to evaluate spin diffusion and spin lifetime. In this work, we demonstrate that this method is no longer accurate when the distance between the inner and outer electrodes is smaller than 6 times the spin diffusion length, leading to errors as large as 50% for the calculation of the spin figures of merit of graphene-based devices. 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 nonlocal spin valves suitable for the flawless determination of the spin lifetime and the spin diffusion coefficient.
Research center :
CESAM - Complex and Entangled Systems from Atoms to Materials - ULiège
Disciplines :
Physics
Author, co-author :
Fourneau, Emile ; Université de Liège - ULiège > Département de physique > Physique des solides, interfaces et nanostructures
Silhanek, Alejandro ; Université de Liège - ULiège > Département de physique > Physique expérimentale des matériaux nanostructurés
Nguyen, Ngoc Duy ; Université de Liège - ULiège > Département de physique > Physique des solides, interfaces et nanostructures
Language :
English
Title :
Roadmap for the Design of All Ferromagnetic Four-Terminal Spin Valves and the Extraction of Spin Diffusion Length
Publication date :
19 March 2021
Journal title :
Physical Review Applied
ISSN :
2331-7019
eISSN :
2331-7043
Publisher :
American Physical Society, College Park, United States - Maryland
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The absence of more than two values for (Equation presented) in spin-valve measurements implies that external electrodes have no impact only if one can prove that all configurations have been probed. For example, only two values for (Equation presented) will be observed if the external electrodes are narrow enough to sustain a large in-plane magnetic field or if each outer electrode has a coercive field similar to that of the closest inner electrode [(Equation presented) and (Equation presented)].
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Using the four variations (Equation presented), (Equation presented), (Equation presented), and (Equation presented), we maintain the orientation of inner electrodes ((Equation presented) and (Equation presented)) and take the four different configurations for the outer electrodes ((Equation presented) and (Equation presented)). As a result, in half of the configurations (Equation presented) injects spin ((Equation presented) and (Equation presented)), while it absorbs for the two other configurations, leading to spin signal generated with an opposite sign. The same reasoning is used for the sign of the spin voltage detected in (Equation presented). Therefore, only the spin signal generated at (Equation presented) and detected at (Equation presented) remains after calculation of the mean of the four signals. The sign of each term in Eq. (1) corresponds to the relative orientation of the two electrodes involved. Thereby, after application of the mean to Eq. (1), only (Equation presented) remains.
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