Variation of magnetism by defects and impurities in two-dimensional magnetic materials based on spin spiral method: A case of δ-(Ga, Mn)As

There is still no effective solution of first-principles calculations to the critical question of how defects and impurities affect magnetism, especially when multi-nearest-neighbor magnetic interactions are involved. In this paper, we use the Heisenberg model and the generalized Bloch condition to evaluate the magnetic interactions of magnetic atoms in various environments. By calculating the dispersion relationship E(q) between the energy E and the wave vector q of the spin spiral in δ-(Ga, Mn)As, the effective multi-nearest neighbor interaction parameters Jxi of Mnx are fitted (x means different types of Mn atoms close to or far away from defects or impurities). The Exi(q) of each kind of Mn sublattice is constructed then with Jxi, and the Curie temperature of each sublattice is obtained by mean field approximation (MFA) and random phase approximation (RPA), respectively. Defect is detrimental to the FM properties at both low and high temperature, while Ga impurity improves FM properties at low temperature by increasing the magnetic stiffness of δ-(Ga, Mn)As. [Display omitted] •In δ-(Ga,Mn)As, Ga substitution is beneficial to increase the magnetic stiffness, while Mn defects weaken the ferromagnetism.•Develop a set of spin spiral methods to study the 2D magnetic system with high concentration of defects or impurities.•We obtained the spin spiral curve of each Mn sublattice, and further obtained the Curie temperature of each sublattice.