Compositional engineering of magnetic anisotropy in Cr2SixGe2-xTe6

Magnetic van der Waals (vdW) materials are highly sensitive to their chemical compositions and atomic structures, which presents rich opportunities for synthetic control of vdW ferromagnets. Here, we synthesized the quaternary alloys Cr2SixGe2-xTe6 using the flux method and discovered that the Ge:Si source ratio should be designed deliberately higher than the expected in resultant crystals due to the stronger affinity of Si than Ge to be involved in Cr2SixGe2-xTe6 reactions. Temperature-dependent magnetization and magnetic hysteresis measurements revealed that as the Si content increases, the Curie temperature decreases while the out-of-plane anisotropy increases monotonically. When x increases from 0 to 2 in Cr2SixGe2-xTe6, the out-of-plane saturation fields remain approximately unchanged at ∼0.2 T, while the in-plane saturation fields increase monotonically from 0.5 T to 1.2 T. The distinct behaviors between out-of-plane and in-plane saturation fields arise from the different mechanisms underpinning the two fields – the out-of-plane saturation field is determined by the competition of exchange interaction, magnetic anisotropy, and dipolar interaction, whereas the in-plane saturation field by magnetic anisotropy. Our compositional engineering provides a fundamental understanding of the layered magnetic materials and insightful guidance for the future design of vdW magnets.