Electrical control of vdW spin materials

2D van-der-Waals (vdW) spin materials have emerged and rapidly flourished in recent years, providing opportunities to open up and advance diverse research areas. One particular direction is the spin-related phenomena, where the current-driven spin-orbit torque (SOT) plays a central role. An ideal SOT spin system requires not only low switching current density and power dissipation, but also field-free switching, which allows for high density, high scalability, easy operation, etc. vdW material Fe₃GeTe₂ (FGT) has been established as a good platform for various SOT physics. However, one drawback in those works is that the SOT switching of spins still inevitably requires the assistance of an external field. In this talk, we demonstrate a novel field-free switching behavior in vdW-spin material/oxide FGT/SrTiO₃ heterostructure. This new field-free switching is possible because the current-driven accumulated spins at the Rashba interface precess around an emergent interface spin moment, eventually producing an ultimate out-of-plane spin polarization. This interpretation is further confirmed by the switching polarity change controlled by the in-plane initialization fields with clear hysteresis. vdW spin material and oxide are successfully combined for the first time, organically exploiting oxide spin physics.

    So far, specific SOT has evolved from FM to collinear AFM, then noncollinear AFM, since AFM spin dynamics have three merits: no stray field; ultrafast THz spin dynamics; weakly coupled to the field. Unfortunately, electrically writing and reading an AFM is extremely challenging, and it is unknown whether current can control a unique type of exotic spin configuration, i.e., helical spin texture. Here, we report the first experimental and theoretical example of the current control of helical AFM in a new vdW material Ni_1/3NbS₂. Theory predicts the electrical control of Ni_1/3NbS₂^'s helical spin texture collectively through macrospin simulations due to the current-driven AFM SOT. Experimentally, we demonstrate such current control in nanometer-thin Ni_1/3NbS₂: resistance change by writing currents; sinusoidal symmetry; transition-like character across T_Neel; and more. Our work constitutes the first demonstration of electrical control of the helical order, combining both theory and experiment.