Mixing A -type and G -type B -site antiferromagnetism in A M n1-x F ex O3 (A=La,Nd)

Using a classical Heisenberg model with anisotropic nearest-neighbor superexchange and uniaxial anisotropy, I investigate the magnetic order of the transition metals on the B sites in AMn1-xFexO3(A=La, Nd; x=[0,1]) with Monte Carlo methods. Magnetic parameters are extracted from preexisting experimental data when available and otherwise estimated with calculations. Superexchange energies are compared to density functional theory and anisotropy energies to ligand field theory, and the potential for doping-induced strain affecting these parameters is considered. I find coexistence regions of different types of magnetic order (A-type and G-type antiferromagnetism), regions with distinct magnetic transitions for the two order parameters, noncollinear ground states for intermediate values of x that decrease the amplitude of the ordered moment in a way consistent with experiment for low dopings, and a reproduction of the experimentally determined, nonmonotonic interpolation of the ordering temperatures. The detailed shape of the phase boundaries in (x,T) space is found to be diagnostic of the magnetic interactions. These results also suggest a ferrimagnetic ground state for the A2MnFeO6 double perovskite with TN≈270K for A=La and Nd.