Marta Galbiati1,2,Florian Godel2,Aymeric Vecchiola2,Victor Zatko2,Hao Wei2,Julian Peiro2,Sergio Tatay1,Regina Galceran2,Alicia Forment-Aliaga1,Eugenio Coronado1,Marie-Blandine Martin2,Bruno Dlubak2,Pierre Seneor2
Universidad de Valencia1,Unité Mixte de Physique CNRS/Thales2
Marta Galbiati1,2,Florian Godel2,Aymeric Vecchiola2,Victor Zatko2,Hao Wei2,Julian Peiro2,Sergio Tatay1,Regina Galceran2,Alicia Forment-Aliaga1,Eugenio Coronado1,Marie-Blandine Martin2,Bruno Dlubak2,Pierre Seneor2
Universidad de Valencia1,Unité Mixte de Physique CNRS/Thales2
In the last years 2D materials have attracted a huge attention thanks to the amazing properties that arise when thickness approaches the single layer level and thanks to the large number of functionalities that they offer. Recently, they started to appear as high potential candidates for spintronics devices since, thanks to their intrinsic two-dimensional nature, they create thin, tuneable and free of defects barriers with sharp interfaces. Despite this potential, investigation of 2D materials for spintronics is still at the beginning. Only very recently few works started to appear using other 2D materials beyond graphene [1,2,3]. In particular, concerning the family of transition metal dichalcogenides (TMDCs), promising theoretical calculations were first reported predicting an extremely large magnetoresistance (MR) signal up to 300% in Fe/MoS<sub>2</sub>/Fe MTJs [4]. However, experimental results are still far from these expectations. Indeed, most of experimental works have to face the main technological issue of avoiding bottom FM electrode oxidation during fabrication process, limiting in turn MR signals.<br/>Here we will show an in-situ fabrication approach to avoid oxidation of the FM electrodes during the device fabrication process that tackles this fundamental problem. We will start reporting the successful fabrication of MoS<sub>2</sub>-based MTJs, investigated as prototypical 2D semiconductive material, then showing perspective on the successful incorporation of more complex, air instable, 2D semiconductors as Black Phosphorous (BP).<br/>The NiFe/MoS<sub>2</sub>/Co MTJs with multilayer MoS<sub>2</sub> mechanically exfoliated flakes we report show the highest results obtained so far for MoS<sub>2</sub>-based spin valve devices [5], thus confirming that our in-situ fabrication protocol allows maintaining high quality non-oxidized interfaces between the ferromagnetic electrodes and the 2D layer.<br/>Beyond interfaces and material quality, we also suggest that an overlooked more fundamental physics issue related to spin-current depolarization could explain the limited MR observed so far in these magnetic tunnel junctions [5,6]. This points to a path towards the observation of larger spin signals in line with theoretical predictions above 100%. We show the impact of our work to be beyond MoS<sub>2</sub> and its broader transition-metal dichalcogenides family by opening the way towards observation of higher magnetoresistance signals and an accelerated screening of other 2D materials that are yet to be explored for spintronics.<br/>[1] W. Wang, A. Narayan, L. Tang et al, Nano Lett., Vol. 15, p. 5261–5267, (2015).<br/>[2] A. Dankert, P. Pashaei, M. Venkata Kamalakar et al., ACS Nano, Vol. 11, p. 6389–6395, (2017).<br/>[3] W.C. Wong, S. M. Ng, H. F. Wong et al., IEEE Trans. Magn., Vol. 53, p.1600205 (2017).<br/>[4] K. Dolui et al., Phys. Rev. B, Vol. 90, p. 041401(R), (2014).<br/>[5] M. Galbiati et al., Phys. Rev. Appl. Vol. 12, p. 044022, (2019).<br/>[6] M. Galbiati et al., ACS Appl. Mater. Interfaces, 10, 30017 (2018).