Magnetic properties of quadruple perovskites containing A- and B-site iron cations

New quadruple perovskites with nominal compositions LnFe4Ti3O12 (Ln = La, Nd) have recently been discovered through high pressure synthesis. Mössbauer spectra show that these materials are AA'3B4O12 materials where the square planar A' sites are occupied by Fe2+ cations while 25% of the octahedral B sites are occupied by Fe3+. Magnetisation data show a transition near 300 K for both materials; also a 10 K transition for Ln = La, and 50 and 12 K anomalies for Ln = Nd. We propose to collect variable temperature (4 - 300 K) neutron powder diffraction from LaFe4Ti3O12 and NdFe4Ti3O12. The POLARIS or GEM diffractometers are suitable for the study of these small samples (0.3 g) resulting from high-pressure synthesis.