Control of Magnetic Easy-axis Rotation by Orbital Angular Momentum of Light
Chun-I Lu1*, Shang-An Wang1, Chak-Ming Liu1, Wen-Chin Lin1, Ting-Hua Lu1, Yann-Wan Lan1
1Department of Physics, National Taiwan Normal University, Taipei, Taiwan
* Presenter:Chun-I Lu,
A field-free programmable spin logic device is the key for developing the magnetic-based logic-in-memories. The heterojunction SiO₂//Pt(5)/Co(0.4)/Ru(1.4)/Co(1.2)/Pt(5 nm) has been shown that the magnetization could be switched and to program the AND, NAND, and NOT logic gate via spin-orbit torque transferring by applying an electrical current [1]. On the other hand, a Laguerre-Gaussian beam (or twisted light), which is a special solution of Maxwell’s Eqs., carries a discrete level of lħ of orbital angular momentum (OAM) per photon. This kind of beam has been demonstrated for several applications, such as optical data storage and quantum communications [2, 3]. In this report, we explore the feasibility of the magnetization switching by using a twisted light. The twisted light is introduced onto the Pt/Co/Ru/Co/Pt and Pd/Co/Pd magnetic heterojunctions' surface. Consequently, we found the hysteresis loops are changed at the long axis, and the angular analysis results show that, the magnetic easy axis is rotated after the twisted light illumination. The mechanism is still under exploring; however, our finding opens a possibility for the twisted light applicate on the magnetic-based logic devices.

[1] Wang, X., et al. Field-Free Programmable Spin Logics via Chirality-Reversible Spin–Orbit Torque Switching. Adv. Mater. 30, 1801318 (2018).
[2] A. Nicolas, L. Veissier, L. Giner, E. Giacobino, D. Maxein, and J. Laurat, A quantum memory for orbital angular momentum photonic qubits, Nat. Photonics 8, 234 (2014).
[3] N. Bozinovic, Y. Yue, Y. Ren, M. Tur, P. Kristensen, H. Huang, A.E. Willner, and S. Ramachandran, Terabit-scale orbital angular momentum mode division multiplexing in fibers, Science 340, 1545-1548 (2013).

This project is financially sponsored by Ministry of Science and Technology of Taiwan
(MOST 108-2112-M-003-010-MY3) and (108-2811-M-003 -509).

Keywords: Twisted Light, Magnetic Anisotropy, Spin-Orbit torque, Spin-Transfer torque, magneto-optics interaction