Strain-Tunable Altermagnetism in Bilayer Perovskites Mediated by Jahn-Teller Distortions.

Altermagnetism, a novel collinear magnetic order distinct from conventional ferromagnetism and antiferromagnetism, has attracted great interest for its unique functional properties and potential applications in ultrafast spintronics. However, achieving effective control of this magnetic order in real materials remains a major challenge. Here, we report that biaxial strain can effectively modulate the altermagnetic order in XCuF3 (X = K and Rb) bilayer perovskites. The modulation is mediated by Jahn-Teller distortion, which introduces the symmetry breaking essential for the altermagnetic state. First-principles calculations reveal that biaxial strain switches the magnetic ground state between the A-type antiferromagnetic and the G-type antiferromagnetic configurations. This magnetic phase transition transforms the band structure from spin degeneracy to spin splitting, thereby activating the altermagnetic response. With the coupling of lattice distortion to altermagnetism, this work provides a paradigm for exploring this phenomenon in perovskites and opens new possibilities for discovering and controlling topological magnetic states in correlated electronic materials.