A molecular-dynamics (MD) theory of itinerant magnetism with complex magnetic structure has been improved by introducing a site-dependent noncollinear effective medium. It takes into account the molecular fields from distant local magnetic moments in a self-consistent way, therefore, allowing us to describe reasonably the temperature dependence of magnetic moments showing complex structures. The theory is applied to γ-Mn with 108 atoms in a MD unit cell. It is demonstrated that the MD approach with the site-dependent medium can describe the second-order phase transition with increasing temperature. Calculated Néel temperature ${(T}_N)$ is shown to be comparable to the experimental value. It is found that the magnetic short-range orders at $T_N$ are rather small, but the 1st and 3rd nearest-neighbor short-range orders show very weak temperature dependence above $T_N.$ The calculated densities of states show a strong temperature dependence below $T_N$ and the peak near the top of the d bands is shown to remain even above $T_N.$

• Received 27 October 1998

DOI:https://doi.org/10.1103/PhysRevB.59.8664