The exploration of non-collinear spin texture in the f-electron-based rare-earth magnets has attracted fascinating interest for its fundamental physics and potential spintronic applications. Here, the real-space observation of nanometric helical spin order with the period down to 20 nm in centrosymmetric TbGa magnets was presented by Lorentz transmission electron microscopy. It was found that the helical period and the initial temperature for the appearance of the periodic helix can be tuned by the thickness of single-crystal TbGa plates (71–169 nm). Furthermore, the domain evolution under the perpendicular magnetic fields and with the shape constriction reveals the high stability of the stripe domains.
