Reversible reorientation of the helimagnetic q-director in a cubic chiral magnet by electric-current polarity

Beyond ferromagnetism, controlling magnetic order using electric current remains a fundamental challenge in condensed-matter physics. In helimagnets, the spatial-modulation vector q represents an active degree of freedom in high-symmetry crystals, yet its deterministic reorientation under current has remained elusive. Here we demonstrate reversible and polarity-selective 90∘ reorientation of the q vector in the cubic chiral magnet Co8.5Zn8.5Mn3. We treat the q orientation as that of a rank-2 director—the symmetry-correct description for helimagnets—rather than as a vector and develop a symmetry-based framework in which the symmetry-allowed combination of current and magnetic field produces q-direction-dependent energy modulations. This mechanism predicts polarity-selective switching, even between orientations oblique to high-symmetry axes, which we directly confirm using in situ Lorentz transmission electron microscopy. Our results establish current polarity as a fundamental control parameter for helimagnetic order. In helimagnets the spatial modulation vector q represents an active degree of freedom in high-symmetry crystals, yet its deterministic reorientation under current is elusive. This paper shows reversible and polarity-selective 90∘ reorientation of the q vector in the cubic chiral magnet Co8.5Zn8.5Mn3