Manipulating spin using contactless and noninvasive optical approaches is one of the forefront topics in modern spintronic science and technology. Prior studies show that optically induced spin reorientation usually scales with spin-orbit coupling strength, setting a limitation on composing heavy elements. In this Letter, we extend such a limit into the nonrelativistic regime by exploring noncollinear magnetic configuration. Using a general spin group-theoretical investigation, we show how the symmetric operators in both spin and lattice spaces control the spin torque and quantum geometry of Bloch wave function—including both quantum metric and Berry curvature. We describe their site-resolved spin symmetries and unravel their selection rules. Furthermore, we adopt a Kagomé lattice model and a realistic material family to showcase the local spin torque under light irradiation. Since the nonrelativistic spin splitting usually spans on the order of electronvolt, significantly larger than typical spin-orbit induced splitting, the nonrelativistic light-induced spin torque is concomitantly much stronger. This Letter extends the previous opto-spintronics from the relativistic to nonrelativistic limit, significantly broadening its realization platform.

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• Antiferromagnetism
• Photoinduced effect
• Noncollinear magnets
• Density functional theory
• Tight-binding model