Figure 2: Tuning of magnetic properties of Teflon tape by mechanical stretching.

(a) Force–strain curve of Teflon tape subjected to mechanical stretch. (b) M–H loop of the original Teflon tape (without stretch). The Teflon tape has a diamagnetic signal. (c) Teflon subjected to mechanical stretch until broken down. No background subtraction has been performed. The ferromagnetic signal is mixed together with the diamagnetic signal. After appropriate correction for the diamagnetic background at high fields, the hysteresis loops were obtained as shown in d. (d) Magnetization curves of as-received Teflon tape (unstretched) and tapes subjected to different strains after the subtraction of the diamagnetic signal (unstretched (violet); 35% strain (red); 60% strain (blue); 100% strain (black)). (e) Measured saturation magnetization in different segments of a stretched Teflon tape from necking point (Segment 1) to the unstretched end of the tape (Segment 4). The typical length and mass of Teflon tapes used in the experiment are 10 cm and 0.08 g, respectively. Each error bar was calculated based on measurements of three samples. (f) Electron spin resonance (ESR) spectroscopy of Teflon tapes under different strains: unstretched and non-magnetic tape (black), Segment 1 (blue) and Segment 4 (red). Segments 1 and 4 are shown in Fig. 1e.