Control of exchange coupling in Co/CoO bilayers on flexible muscovite substrate by bending strain

Thai Duy Ha^1*, Yu-Hong Lai², Chun-Fu Chang³, Shang-Fan Lee⁴, Liu-Hao Tjeng³, Jenh-Yih Juang¹, Ying-Hao Chu^1,2,4

¹Electrophysics, National Chiao Tung University, HSINCHU, Taiwan
²Materials Science and Engineering, National Chiao Tung University, HSINCHU, Taiwan
³Chemical Physics of Solids, Max-Planck Institute, DRESDEN, Germany
⁴Institute of Physics, Academia Sinica, Taipei, Taiwan

* Presenter:Thai Duy Ha, email:duyht0104@gmail.com

The use of flexible muscovite as the substrate has given rise to applying strains to films by mechanical bending method. In this study, we take advantage of this novel approach to investigate the strain effects of bending to ferromagnetic/anti-ferromagnetic (FM/AFM) bilayers deposited on mica substrates. Two different Co5 nm/CoO30 nm bilayer heterostructures on flexible muscovite mica substrate were prepared by oxide molecular beam epitaxy with (111) or (100) orientation of CoO layer. Due to the mechanical flexibility of the heterostructure, the effect of bending strain on Co/CoO bilayers was investigated. Strain-dependent exchange-bias behaviors of the bilayers indicated that the effects only existed on the sample of Co/CoO(100) and seemed not appear for Co/CoO(111). The origin was attributed to the spin re-orientation in Co/CoO(100) bilayer. The strain-dependent pinning directions of the bilayers were determined by anisotropic magneto-resistance (AMR) technique to confirm this. This provides us fundamental understanding of strain-dependent magnetic exchange coupling and a novel approach to study strain effect as well as to develop flexible spintronics devices.

Keywords: Exchange coupling, Bending strain, Strain effect, Muscovite