MS28-P02 Neutron powder diffraction study of Tm2Mn2O7 and Y2Mn2O7 - pyrochlore obtained by yet another chemical route of synthesis Ekaterina Pomjakushina (Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen, Switzerland) Katharina Rolfs (Laboratory for Development and Methods, Paul Scherrer Institut, Villigen, Switzerland) Janusz Karpinski (Laboratory for Development and Methods, Paul Scherrer Institut, Villigen, Switzerland) Kazimierz Conder (Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen, Switzerland) Vladimir Pomjakushin (Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Villigen, Switzerland)email: ekaterina.pomjakushina@psi.ch
The rare earth manganese (IV) pyrochlores cannot be synthesized at ambient pressure requiring high pressures for the stabilization of the pyrochlore lattice, which is mainly due to the small size of Mn (IV) compared to trivalent rare earth cations.  All of these materials appear to be ferromagnets. Neutron studies of some selected A2Mn2O(Y, Ho, Yb) were done, but still more work is needed to completely characterize their magnetic ground state. We present yet another chemical way of synthesis of Tm2Mn2O[1] and Y2Mn2O[2] pyrochlores and the studies of their magnetic and crystal structures by high resolution neutron powder diffraction. Both compounds are single phase pyrochlores (Fd3-m) at room temperature. On cooling below about 30K they show the transitions to the ferromagnetic state with additional antiferromagnetic (AF) canting on only one sort of atoms for Tm2Mn2O7. The magnetic structure has magnetic Shubnikov group I41/am′d′ with the tetragonal distortion and large magnetostrsiction (especially for A=Y) refined from the diffraction data. The presence of AF canting in both compounds with magnetic (Tm) and nonmagnetic (Y) A-cation allows us to assign AF-ordering to Mn-sublattice.
References:

[1] E. Pomjakushina et al,  (2015) Inorganic Chemistry, 54,  9092

[2] V. Pomjakushin et al, to be published

Keywords: magnetic structure, pyrochlore