Magnetism and spin exchange coupling in strained monolayer CrOCl

The magnetism and spin exchange coupling of monolayer CrOCl with different strains are investigated systematically using first principles. It is found that the magnetic ground state can be changed from ferromagnetic (FM) to antiferromagnetic (AFM), and the Curie temperature (Tc) is enhanced significantly by applying the uniaxial strain along a- or b-axis direction. The variations of spin exchange coupling are explained according to the Goodenough-Kanamori-Anderson (GKA) and Bethe-Slater Interaction (BSI) rules. The strain-dependent magnetic state is mainly attributed to the competition between direct exchange interactions of cation-cation and indirect superexchange ones of cation-anion-cation in monolayer CrOCl. The different competitions in a- and b-axis direction determine the different critical intervals R for magnetic state transitions, where R is the distance of the two nearest-neighbor (NN) Cr3+ ions. The AFM-FM transition occurs at R/r3d=2.9 and 3.75 in a-axis direction, while it happens at R/r3d=2.65 along b-axis direction. These results indicate that the sensitive relevancy between the external strain and magnetic coupling makes monolayer CrOCl a promising candidate for spintronics.