Persistence of local-moment antiferromagnetic order in Ba _1-xK_xMn₂As₂

BaMn₂As₂ is a local-moment antiferromagnetic insulator with a Néel temperature T_N of 625 K and a large ordered moment of 3.9 μ_B/Mn. Remarkably, this compound can be driven metallic by the substitution of as little as 1.6% K for Ba while retaining essentially the same ordered magnetic moment and Néel temperature, as previously reported. Here, using both powder and single crystal neutron diffraction we show that the local moment antiferromagnetic order in Ba_1-xK_xMn₂As₂ remains robust up to x=0.4. The ordered moment is nearly independent of x for 0 ≤x≤ 0.4 and T_N decreases to 480 K at x=0.4.