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Strain-controlled switch between ferromagnetism and antiferromagnetism in 1T-CrX2 (X = Se, Te) monolayers

We report on the strain-induced switch between ferromagnetic (FM) and antiferromagnetic (AFM) orderings in 1T-CrX2 (X = Se, Te) monolayers based on the first-principles calculations. The CrSe2 and CrTe2 monolayers without strains are found to be AFM and FM, respectively. Under the biaxial tensile strain, the CrSe2 monolayer tends to be FM when the strain is larger than 2%. The FM state is further stabilized when the strain is increased. Moreover, the CrSe2 monolayer changes to be half-metallic when the tensile strain is larger than 10%. While for the CrTe2 monolayer, the critical strain at which the transition between the FM and AFM states occurs is compressive, of -1%. Relatively small tensile strains of 4% and 2%, respectively, can enhance the Curie temperature of CrSe2 and CrTe2 monolayers above the room temperature. The strain-induced switch between the FM and AFM states in CrSe2 (CrTe2) monolayer can be understood by the competition between the AFM Cr-Cr direct exchange and FM Cr-Se(Te)-Cr superexchange interactions. The tunable and attractive magnetic and electronic properties controlled by the flexible strain are desirable for the future nanoelectronic applications.