Ferroelastic altermagnetism

Combination of altermagnetism and ferroic orders, such as ferroelectric switchable altermagnetism [ Phys. Rev. Lett . 134 , 106801 (2025) and Phys. Rev. Lett . 134 , 106802 (2025)], offers a powerful route to achieve nonvolatile switching of altermagnetic spin splitting. In this work, by synergizing altermagnetism and ferroelasticity, we propose the concept of ferroelastic altermagnets in which the ferroelastic crystal reorientation can drive multistate nonvolatile switching of the altermagnetic spin splitting via altermagnetoelastic effect . Using monolayers RuF 4 and CuF 2 as material candidates, we demonstrate 2-state and 3-state altermagnetic spin splitting switching as driven by ferroelastic strain states. Transport calculation shows that multistate spin conductivities can be ferroelastically encoded in ferroelastic altermagnets, thus suggesting the potential of ferroelastic altermagnets as nonvolatile nanomechanical spin switches. The proposed concept of ferroelastic altermagnetism enriches the emerging landscape of multiferroic altermagnetism and shall pave a way towards straintronic-spintronic device applications.