In this work we present a new chemical route to synthesize Tm2Mn2O7 pyrochlore, a compound which is thermodynamically unstable at ambient pressure. Differently from the reported in the past high pressure synthesis of the same compound applying oxides as starting materials, we have obtained a pure phase Tm2Mn2O7 by a converting TmMnO3 at 1100 C and 1300 bar oxygen pressure. The studies of Tm2Mn2O7 performed by a high resolution neutron powder diffraction have shown, that a pure pyrochlore cubic phase Tm2Mn2O7 (space group Fd-3m) have been obtained. On cooling below 25K there is a transition to a ferromagnetically (FM) ordered phase observed with an additional antiferromagnetic (AFM) canting suggesting a lowering of the initial cubic crystal symmetry. The magnetic transition is accompanied by small but well visible magnetostrsiction effect. Using symmetry analysis we have found a solution for the AFM structure in the maximal Shubnikov subgroup I41/am'd'.
@article{arxiv.1507.02830,
title = {New synthesis route and magnetic structure of Tm2Mn2O7 - pyrochlore},
author = {Ekaterina Pomjakushina and Vladimir Pomjakushin and Katharina Rolfs and Janusz Karpinski and Kazimierz Conder},
journal= {arXiv preprint arXiv:1507.02830},
year = {2015}
}