We demonstrate a deterministic switching mechanism in collinear altermagnets driven by asymmetric sublattice spin currents. Unlike conventional antiferromagnets, where combined parity-time reversal symmetry enforces purely staggered sublattice spin torques, altermagnets host symmetry-protected nonrelativistic spin splitting that produces unequal torques on the two sublattices. Using doped ${\mathrm{FeSb}}_2$ as a representative $d$-wave altermagnet, our Landau-Lifshitz-Gilbert simulations show that these torques enable magnetic field-free and deterministic ${180}^{\circ }$ Néel vector reversal over picosecond timescale. The mechanism is generic to even-parity altermagnets and remains effective even in centrosymmetric, weak spin-orbit coupled altermagnets, where the Néel spin-orbit torque mechanism fails. Our results establish an experimentally accessible mechanism for switching of altermagnetic order, opening pathways for realizing ultrafast, low-power altermagnet spintronic devices.

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• Spin torque
• Transport phenomena
• Antiferromagnets
• Landau-Lifschitz-Gilbert equation