Complex magnetic ordering behavior in the frustrated perovskite Ba2MnMoO6

New and exotic ground states of magnetic materials are highly sought after extensively studied for the insights they provide into thermodynamics disorder fundamental interactions. By controlling crystal structure an appropriate lattice, it is possible to cause strong exchange interactions sum zero so be frustrated. Due presence this frustration, lowest energy configuration that results may crucially dependent on tiniest differences between a multitude have (almost) same energy. The keen interest in these arises from fact finely balanced systems offer way probing classical or quantum mechanical importance but too weak observed non-frustrated systems. Here, we combine local crystallographic probes cation-ordered double perovskite Ba2MnMoO6 contains face-centered cubic lattice S = 5/2 Mn2+ cations. Neutron diffraction measurements below 9.27(7) K indicate fourfold degenerate non-collinear antiferromagnetic state exists with almost complete ordering spins. Muon spin relaxation probe fields inside material over t1/2 2.2 µs lifetime muon, indicating slightly lower Néel transition temperature 7.9(1) K. dc susceptibility data do not show loss magnetization should accompany onset order; strongly antiferromagnetically coupled paramagnetic [θ −73(3) K] persists down 4 K, at which occurs. behavior differs considerably closely related compositions Ba2MnMO6 (M W, Te), collinear arrangements well defined transitions bulk susceptibility. This suggests Mo6+ cation leads fine balance nearest next-nearest neighbor superexchange frustrated structures.