Linear magnetoelectricity in the Zintl phase pnictides (Ba, Ca, Sr)Mn_2(P, As, Sb)_2 from first principles calculations

We report a comprehensive set of density functional theory calculations on the family of layered antiferromagnetic manganese pnictides (Ba, Ca, Sr)Mn_2(P, As, Sb)_2. We characterize all components to the linear magnetoelectric (ME) tensor α which are parsed into their contributions from spin and orbital moments for both lattice-mediated and their clamped-ion electronic analogs. Our main results show that the orbital magnetization components cannot be neglected in these systems. The ME response is dominated by electronic effects with total α values exceeding those of the prototypical Cr_2O_3 (i.e. α≃ 6.79 ps/m in BaMn_2As_2). We also identify a strong correlation with the computed ME susceptibility on pnictogen substitution in the trigonal subfamily albeit with weaker amplitudes (α≃ 0.2-1.7 ps/m). Additionally, we provide the dependence of these predictions on the Hubbard +U correction, at the level of the local density approximation, which show large variations on the calculated ME coefficients in the tetragonal compounds highlighting the role of strong correlation in these compounds.