Strain-Induced Tunable and Field-Free Spintronic THz Emitters Based on Flexible Substrate Heterostructures

Area of Science:

• Terahertz (THz) science and technology
• Spintronics
• Materials science

Background:

• Spintronic terahertz (THz) emitters offer broadband frequency, high efficiency, and simple fabrication.
• THz signal intensity is typically proportional to ferromagnetic (FM) layer magnetization and requires an external magnetic field.
• Existing field-free THz emitters are rare, especially those based on common FM/nonmagnetic metal structures.

Purpose of the Study:

• To fabricate a tunable and field-free THz emitter with significant modulation capabilities.
• To investigate the effect of substrate curvature on THz emission.
• To explore a novel approach for designing field-free spintronic THz sources.

Main Methods:

• Fabrication of a polyimide/CoFeB/Pt heterostructure.
• Modulation of THz emission by altering the curvature radius of the polyimide substrate.
• Analysis of THz radiation intensity in flat, forward-bent, and backward-curved states.

Main Results:

• A tunable, field-free THz emitter based on a polyimide/CoFeB/Pt heterostructure was successfully fabricated.
• Forward bending induced tensile strain, leading to in-plane magnetic anisotropy and enhanced THz emission without an external magnetic field.
• Backward bending sharply decreased THz intensity, with over 95% modulation achieved between forward-curved and backward-curved states.
• The device demonstrated good cyclic repeatability.

Conclusions:

• A novel method for designing field-free spintronic THz sources was presented.
• The flexible THz emitter shows promise for applications in THz devices.
• Strain-induced magnetic anisotropy offers a new pathway for controlling spintronic THz emission.