Effect of thermal noise on the field-assisted spin-orbit-torque-driven dynamics in Mn₃Sn

D0₁₉-Mn₃Sn, an antiferromagnet (AFM) with a non-collinear spin structure, has recently been investigated for its large anomalous Hall effect, low-current dynamics, and as a source of spin-polarized current. Thin films of Mn₃Sn, when grown epitaxially on MgO (110) [001], experience a uniaxial tensile strain. Consequently, the bulk six-fold anisotropy changes to a two-fold perpendicular magnetic anisotropy (PMA). Prior numerical works have examined SOT-driven deterministic dynamics in PMA Mn₃Sn in the presence of a symmetry-breaking magnetic field at . They find the final steady-state to depend on the magnitude of the input current, , with respect to two critical currents (J_c^th1 and J_c^th2). The magnetic octupole switches from one stable state to another for J_c > J_c^th1 whereas it exhibits chiral rotations, whose frequency could be tuned from MHz-GHz, if J_c > J_c^th2. These works, however, do not consider the role of thermal noise either in the equilibrium state or during the dynamics. Therefore, in our work, we solve coupled LLG equations in the presence of a thermal field. Consequently, the equilibrium states show a Gaussian distribution around ϕ_oct =±π/2. We find the standard deviation to be directly related to the temperature, T, and inversely related to the volume, Vand the saturation magnetization, M_s. The octupole exhibits stochastic dynamics and switches (oscillates) even for J_c < J_c^th1 (J_c < J_c^th2). We expect the insights of our investigation to be useful to both experimentalists and device designers.