Small-scale magnetic field measurements from ZeeTurbo (Cristofari et al. 2023) using SPIRou spectra for AU Mic, EV Lac, GJ1289, and Gl 410, along with their periodograms. The black horizontal lines (solid, dashed, dotted) indicate false alarm probabilities of 10%, 1%, and 0.1%. The vertical blue dashed line marks the literature rotation period. The gray curve represents the window function, illustrating time sampling effects.