Double and double double perovskites in the RMnMnTaO6 series
Kunlang Ji, Yahua Yuan, G.T. Moyo, C. Ritter, J. Paul Attfield
Abstract
A new family of perovskites RMnMnTaO6 has been synthesised at high pressure for representative R = La, Nd, Sm, Eu, Gd, Y and Lu that span the whole rare earth series. The structure type changes from tetragonal P42/n double double perovskite (DDPv) type with columnar R3+/Mn2+ cation order (R = La, Nd, Sm) to monoclinic P21/n double perovskite (DPv) (R0.5Mn0.5)2MnTaO6 (R = Sm, Gd, Y, Lu) as R3+ cation size decreases. No antisite disorder or nonstoichiometry is observed. Spin ordering transitions are observed below 70 K and a neutron diffraction study of DDPv NdMnMnTaO6 reveals ferrimagnetic orders at TC1 = 65 K and TC2 = 40 K with Mn-spin reorientation due to Nd moment order at TC2 leading to magnetoelastic coupling.