Tuning Isolated Zero-field Skyrmions and Spin Spyrals at Room-temperature in Synthetic Ferrimagnetic Multilayers

Jeovani Brandão¹, Danian A. Dugato^1,2, Marcos V. Puydinger dos Santos³, Fanny Béron³, Júlio C. Cezar¹

¹Labraťorio Nacional de Luz Śincrotron (LNLS), Centro de Pesquisa em Energia e Materiais (CNPEM), Brazil
²Departamento de Física Universidade Federal de Santa Maria, Brazil
³Institute of Physics “Gleb Wataghin”, University of Campinas, Brazil

Antiferromagnetic spintronics is a promising alternative to ferromagnetic systems, mainly due to the absence of stray fields and possibilities of operating in the terahertz regime. However, AFM materials inherently difficult the magnetic spins control by currents and/or magnetic fields. Recently ferrimagnetic materials, which consist of anti-parallel yet uncompensated magnetic sublattices, emerged as a suitable solution. Here, the objective was to observe individual skyrmions at room-temperature and under null external magnetic field in ferrimagnetic multilayers. The study, performed in collaboration of the Brazilian Synchrotron Light Laboratory (LNLS), showed through element specific X-ray magnetic circular dichroism (XMCD) that uncompensated ferrimagnetic orientation between Co and Gd atoms remains in synthetic Pt/CoGd/Pt ferrimagnetic multilayers with sub-nanometer thick [1]. While spin spyrals were observed by magnetic force microscopy for thicker CoGd layers ≥ (1.2 nm), the tunable enhanced perpendicular magnetic anisotropy and remanent magnetization leads to isolated zero-field skyrmions for thinner CoGd ≥ (0.9 nm). The demonstration of stable skyrmions in perpendicularly magnetized materials with antiparallel exchange-coupling is a promising step towards future antiferromagnetic-based devices for spintronics applications.

Financial support: Brazilian agencies FAPESP (Project No. 2012/51198-2, 2017/10581-1, and 2020/07397-7) and CNPq (303344/2017-2, 436573/2018-0, 312762/2021-6).

References:
[1]   J. Brandao, D.A. Dugato, M.V. Puydinger dos Santos et al., “Tuning isolated zero-field skyrmions and spin spyrals at room-temperature in synthetic ferrimagnetic multilayers”, Applied Surface Science, vol. 585, p. 152598, 2022, https://doi.org/10.1016/j.apsucs.2022.152598.