Atomic-scale understanding of high thermal stability of the Mo/CoFeB/MgO spin injector for spin-injection in remanence

• Published in: Nanoscale Vol. 10; no. 21; pp. 10213 - 10220
• Main Authors: Tao, Bingshan, Barate, Philippe, Devaux, Xavier, Renucci, Pierre, Frougier, Julien, Djeffal, Abdelhak, Liang, Shiheng, Xu, Bo, Hehn, Michel, Jaffrès, Henri, George, Jean-Marie, Marie, Xavier, Mangin, Stéphane, Han, Xiufeng, Wang, Zhanguo, Lu, Yuan
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 01.01.2018
• Subjects: Annealing; Atomic structure; Circular polarization; Condensed Matter; Diffusion barriers; Diffusion layers; Electroluminescence; Injectors; Light emitting diodes; Magnesium oxide; Magnetic anisotropy; Magnetic properties; Optoelectronics; Physics; Remanence; Thermal stability
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c8nr02250j

Remanent spin injection into a spin light emitting diode (spin-LED) at zero magnetic field is a prerequisite for future application of spin optoelectronics. Here, we demonstrate the remanent spin injection into GaAs based LEDs with a thermally stable Mo/CoFeB/MgO spin injector. A systematic study of magnetic properties, polarization-resolved electroluminescence (EL) and atomic-scale interfacial structures has been performed in comparison with the Ta/CoFeB/MgO spin injector. The perpendicular magnetic anisotropy (PMA) of the Mo/CoFeB/MgO injector shows more advanced thermal stability than that of the Ta/CoFeB/MgO injector and robust PMA can be maintained up to 400 °C annealing. The remanent circular polarization (PC) of EL from the Mo capped spin-LED reaches a maximum value of 10% after 300 °C annealing, and even remains at 4% after 400 °C annealing. In contrast, the Ta capped spin-LED almost completely loses the remanent PC under 400 °C annealing. Combined advanced electron microscopy and spectroscopy studies reveal that a large amount of Ta diffuses into the MgO tunneling barrier through the CoFeB layer after 400 °C annealing. However, the diffusion of Mo into CoFeB is limited and never reaches the MgO barrier. These findings afford a comprehensive perspective to use the highly thermally stable Mo/CoFeB/MgO spin injector for efficient electrical spin injection in remanence.