Strain-induced altermagnetism to ferromagnetism transition in monolayer Cr 2 Si 2 S 3 Se 3

Magnetic phase transition, especially that involving altermagnets, can provide diverse mechanisms and ideas for the development of multifunctional materials. Here, we employ first-principles calculations to predict the altermagnetic monolayer Cr2Si2S3Se3 with excellent stability. The Cr2Si2S3Se3 is an indirect bandgap semiconductor, which features i-wave spin splitting symmetry due to the spin layer group of 1 32 m. Tensile strain can induce a phase transition from altermagnetism to ferromagnetism, with the critical strain ratio a/a0 being 1.02. This phase transition causes the spin splitting to evolve from momentum-dependent one to global one (i-wave to s-wave). When spin-orbital coupling is taken into account, the magnetic phase transition is also accompanied by the disappearance of the valley polarization between the -K and K valleys. Our works broaden the scope of magnetic phase transitions and highlight the connection with valley polarization, which is beneficial for the integration of spintronics and valleytronics.