Tuning magnetic anisotropy and Curie temperature in two-dimensional half-metal CoOBr via alloying strategy

Two-dimensional (2D) half-metallic materials hold great promise for spintronic applications, yet their practical implementation is often hindered by relatively low Curie temperature (Tc) and limited magnetic anisotropy energy (MAE). In this paper, we systematically study the intrinsic electromagnetic properties of the CoOBr monolayer and further investigate the effect of Co site Ir substitution on the formation of the CoIrO2Br2 structure. It indicates that the CoOBr monolayer exhibits typical half-metallic behavior with a Curie temperature (Tc) of 109 K. The easy magnetization axis (EMA) of CoOBr lies in the plane, with the minimum MAE of −0.55 meV per unit cell along the y-axis. Upon Ir substitution, the CoIrO2Br2 monolayer retains its half-metallic character while showing significantly enhanced magnetic properties, with the Tc markedly increased to 409 K. The EMA remains in-plane, accompanied by strongly enhanced magnetic anisotropy, where the MAE reaches −2.72 and −1.84 meV per unit cell along the x-axis and y-axis, respectively. This change induces the opening of the spin wave bandgap, thereby enhancing the stability of the magnetic sequence. This study reveals that elemental substitution provides an effective strategy for tuning the Tc and magnetic anisotropy characteristics in CoOBr-based 2D systems, offering useful insights into the modulation of magnetic properties in low-dimensional materials.