We investigate the influence of in-plane tensile strain on the magnetic ground state and spin-orbit torque (SOT)-driven magnetization processes in $\mathrm{M}{\mathrm{n}}_3\mathrm{Sn}$ thin films using atomistic spin modeling. Our study reveals that strain acts as a critical tuning parameter, inducing a transition from the $E_{1g}\left(A_x\right)$ to the $E_{1g}\left(A_y\right)$ magnetic structure beyond a threshold strain corresponding to a reduction of the exchange interaction $\left|\delta \mathrm{J}\right|\approx 2\%$. This transition is significant as the $E_{1g}\left(A_y\right)$ state is expected to support a large anomalous Hall effect, enabling strain-controlled topological transport properties. Additionally, tensile strain breaks the symmetry between antiferromagnetic sublattices, leading to a piezomagnetically induced net magnetization that increases linearly with strain and is oriented perpendicular to the film plane. Under SOT excitation, $\mathrm{M}{\mathrm{n}}_3\mathrm{Sn}$ under strain exhibits sharp, deterministic switching of the cluster octupole moment with a reduced threshold current density, highlighting enhanced SOT efficiency. In contrast, the strain-free system shows intermediate chiral spin rotations during the switching of the octupole moment. Dynamic simulations further reveal current-density-dependent distinct precession modes, including a transient optical mode within a narrow current density range and ultrafast precessions reaching terahertz frequencies. These findings demonstrate the potential of strain engineering to tailor magnetic ground states and achieve low-energy, high-speed magnetization control in noncollinear antiferromagnets. The resulting functionalities offer promising avenues for scalable spintronic devices operating at terahertz frequencies.

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• Magnetism
• Spin dynamics
• Spintronics
• Topological materials
• Ultrafast magnetic effects