Carrier and thickness mediated ferromagnetism in chiral magnet Mn1/3TaS2 nanoflakes

Layered chiral magnets with broken spatial inversion symmetry (SIS) enable chiral spin textures to occur in atomically thin layers. However, most layered materials retain SIS during their crystallization. Here, we demonstrate that SIS can be broken in a layered transition metal dichalcogenide TaS2 by intercalating Mn atoms. A chiral magnetic phase in Mn1/3TaS2 has, thus, been realized. This phase enables a nonzero Dzyaloshinskii–Moriya interaction, which in turn gives rise to large topological Hall effects (THEs) below 50 K. Both the ferromagnetism and THE can be tuned at low temperatures by modulating the carrier density via a protonic gate. Measured at 20 K with Vg = −4.7 V applied to the gate and electron doping density of 1.7 × 1022 cm−3, the maximum THE was almost double that recorded with no gate voltage applied. By further reducing the sample thicknesses, both the Curie temperature Tc and the longitudinal magnetoresistance can be significantly modulated. This is consistent with the theory of critical behavior. Our work highlights the ability to control both magnetism and chiral spin textures in Mn1/3TaS2 nanoflakes. Applying this discovery may lead to a variety of practical van der Waals heterostructure devices.