The ability to control the direction in which a signal travels – without external switching, without added circuitry – is a longstanding goal in the design of compact magnetic devices. Magnetochiral anisotropy offers exactly that: a material-level asymmetry in which magnetic waves (known as magnons) travelling in opposite directions are physically inequivalent, opening a route to magnetic logic operations and memory that retains data without a continuous power supply. The effect has been understood in principle for decades, but always felt like a phenomenon that nature deliberately made inconvenient. Accessing magnetochiral anisotropy required materials that are chiral at the crystalline level – compounds like Cu2OSeO3, where the Dzyaloshinskii-Moriya interaction (DMI, a quantum mechanical force that pushes neighbouring magnetic moments to twist relative to each other) emerges only from a non-centrosymmetric crystal lattice that takes considerable effort to synthesize.…